A farmer asks an educated man whether a hen came first or an egg came first. Give your answer on the basis of the concept of evolution.

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 and Curd.

Arrange the following elements in the increasing order of their first ionisation potentials, give proper explanation for your answer. a) Li, Be, B b) N, O, F c ) C, N, O, F