Question

Which of the following has only unidirectional flow?

• A. Energy
• B. Carbon
• C. Sulfur
• D. Nitrogen

Answer 1

The correct option is A

Energy

The correct option is A.

The explanation for the correct option :

1. Energy flow is the drift of energy at different levels.
2. It takes place through the food chain and the food web.
3. Energy is either lost in the form of heat or transported from one level to another.

The explanation for the incorrect options

Option B:

1. The flow of carbon in nature is not unidirectional as carbon in the form of carbon dioxide is released by humans during respiration, which is absorbed by plants and used for breathing and photosynthesis.
2. Carbon is also released by the burning of fuels.

Option C:

Sulfur enters the atmosphere through human activities mostly because of industrial processes and returns to the surface of the earth in the form of acid rain.

Option D:

Nitrogen is absorbed by plants and animals through nitrogen fixation or by converting it to different chemical forms such as ammonia and it is released back into the atmosphere through combustion.

Final answer: Energy has unidirectional flow.