Question

Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer.

Biogas, Citric acid, Penicillin, Curd.

Answer 1

Penicillin is an antibiotic that helps to kill pathogens that cause infections and diseases and thus, saves lives.

Biogas is a non-polluting clean fuel that is produced as a byproduct of sewage treatment. It is used for cooking and lighting up the homes in rural areas.

Curd has good nutrient value, provides $vitamin-B_{12}$ and replaces harmful bacteria of the stomach with helpful ones.

Citric acid it is used as the preservative of food.