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Choose the incorrect statement from the following. A good fuel is one which: (a) is readily available. (b) produces a large amount of heat. (c) leaves behind many undesirable substances. (d) burns easily in the air at a moderate rate.

(c) leaves behind many undesirable substances. Any substance which upon combustion produces a usable amount of energy is known as... View Article

Marked temperature changes in aquatic environment can affect (a) breeding of animals (b) more growth of aquatic plants (c) process of digestion in animals (d) availability of nutrients.

a) Breeding of animals Explanation Marine ecosystem covers the largest surface area of the earth. Two third of earth is... View Article

The process of nitrogen-fixation by bacteria does not take place in the presence of (a) molecular form of hydrogen (b) elemental form of oxygen (c) water (d) elemental form of nitrogen

b) Elemental form of oxygen Explanation Nitrogen fixation is the essential biological process and the initial stage of the nitrogen... View Article

If you live in an overcrowded and poorly ventilated house, it is possible that you may suffer from which of the following diseases (a) Cancer (b) AIDS (c) Air borne diseases (d) Cholera

a)Airborne disease Explanation The diseases which are transmitted through contaminated air are known as airborne diseases. When the person lives... View Article

The feature that is not a characteristic of protochordata? (a) Presence of notochord (b) Bilateral symmetry and coelom (c) Jointed legs (d) Presence of circulatory system (e) Both c and d

e) Both C and D Explanation Protochordate is an informal category of organisms to describe the invertebrates that are closely... View Article

Survival of plants in the terrestrial environment has been made possible by the presence of (a) intercalary meristem (b) conducting tissue (c) apical meristem (d) parenchymatous tissue

(b) conducting tissue The conducting tissues in plants conduct different saps and have different structures. The primary conducting tissues or plants... View Article

In villages, people use wood as fuel because: (a) it is considered to be an ideal fuel. (b) of its easy availability and low cost. (c) it is environment-friendly. (d) it catches fire easily.

(b) of its easy availability and low cost. Explanation In villages, people use wood as fuel because: (a) it is... View Article

We should not allow mosquitoes to breed in our surroundings because they (a) multiply very fast and cause pollution (b) are vectors for many diseases (c) bite and cause skin diseases (d) are not important insects

b) Are vectors for many diseases. Explanation Mosquitoes can transmit diverse infectious pathogens and parasites that cause diseases such as dengue,... View Article

Which of the following statements are not true for eukaryotic cells? (i) They do not have a nuclear membrane. (ii) They have a well-organised nucleus. (iii) They have a nuclear membrane. (iv) Blue-green algae are eukaryotic cells

(ii) and (iii) The eukaryotic cells are the advance cells that have a well-defined nucleus that is surrounded by a... View Article

Paheli prepared a blue coloured solution of copper sulphate in beaker A and placed an iron nail in it. Boojho prepared a yellowish-green solution of ferrous sulphate in beaker B and placed a copper wire in it. What changes will they observe in the two beakers after an hour?

In beaker A, a reddish brown layer of copper will deposit on the iron nail and the blue coloured solution... View Article

If cells of onion peel and RBC are separately kept in hypotonic solution, what among the following will take place? Explain the reason for your answer. (a) Both the cells will swell. (b) RBC will burst easily while cells of onion peel will resist the bursting to some extent. (c) a and b both are correct. (d) RBC and onion peel cells will behave similarly.

c) Both a and b Explanation The solution with higher concentration of water as compared to the cell is termed... View Article

Top-soil contains the following (a) Humus and living organisms only (b) Humus and soil particles only (c) Humus, living organisms and plants (d) Humus, living organisms and soil particles.

d) Humus, living organisms and soil particles. Explanation The soil is the topmost layer of the earth’s crust mainly composed... View Article

A substance which reacts with oxygen giving heat is called a combustible substance. Which one of the following is a combustible substance? (a) iron nail (b) glass (c) stone piece (d) wood

(d) wood Combustible substances are the substance which burn in air to produce heat and light are called combustible substances.... View Article

(a) Conversion of solid to vapour is called sublimation. Name the term used to denote the conversion of vapour to solid. (b) Conversion of solid state to liquid state is called fusion; what is meant by latent heat of fusion?

(a) It is also called sublimation. The term sublimation is the passage or the transformation or conversion that substances undergo... View Article

Which one of the following sets of phenomena would increase on raising the temperature? (a) Diffusion, evaporation, compression of gases (b) Evaporation, compression of gases, solubility (c) Evaporation, diffusion, expansion of gases (d) Evaporation, solubility, diffusion, compression of gases

(c) Evaporation, diffusion and expansion of gases Evaporation, diffusion and expansion of gases increase on raising the temperature. Evaporation rate... View Article

Select the odd one out (a) The movement of water across a semi-permeable membrane is affected by the amount of substances dissolved in it. (b) Membranes are made of organic molecules like proteins and lipids (c) Molecules soluble in organic solvents can easily pass through the membrane. (d) Plasma membranes contain chitin sugar in plants

d) Plasma membranes contain chitin sugar in plants. Each cell is bounded by an extremely delicate, thin elastic living membrane, called... View Article

Among the given options, which one is not correct for the use of a large amount of fertilisers and pesticides? (a) They are eco-friendly (b) They turn the fields barren after some time (c) They adversely affect the useful component from the soil (d) They destroy the soil fertility

a) They are eco-friendly Explanation Pesticides are chemical substances that are meant to kill pests. In general, a pesticide is a... View Article

Choose the correct statement of the following (a) Conversion of solid into vapours without passing through the liquid state is called sublimation. (b) Conversion of vapours into solid without passing through the liquid state is called vaporisation. (c) Conversion of vapours into solid without passing through the liquid state is called freezing. (d) Conversion of solid into liquid is called sublimation.

b) Conversion of solid into vapours without passing through the liquid state is called sublimation. Conversion of solid into vapours... View Article

During adolescence, the body of boys and girls undergoes certain changes. Given below are a few of those changes. (a) Broad shoulders (b) Wider chests (c) The wider region below the waist (d) Development of muscles (e) Development of mammary glands (f) Growth of facial hair (g) Acne and pimples on the face (h) Development of sex organs (i) High-pitched voice (j) Growth of pubic hair. Categorise these changes according to their occurrence in boys and those that occur in girls and fill in the table given below.

Boys Girls Broad Shoulders Wider region below waist Wilder Chest Development of mammary glands Growth of muscles Acne and pimples... View Article

Low visibility during cold weather is due to (a) formation of fossil fuel (b) unburnt carbon particles or hydrocarbons suspended in air (c) lack of adequate power supply (d) none of these

b) unburnt carbon particles or hydrocarbons suspended in air Explanation The visibility of forming fog is lowered during winter is... View Article

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