The method of incorporating desirable characters into crop varieties is by

Write two examples each of the fishes that are:
$(i)$ Top dwellers
$(ii)$ Middle dwellers
$(iii)$ Bottom dwellers,in composite fish culture.

$(a)$ Distinguish between macronutrients and micronutrients on the basis of $(i)$ their functions and $(ii)$ amount required by plants. $(b)$ Classify the following elements as macro or micronutrients in plants: $(i)$ Nitrogen,$(ii)$ Zinc,$(iii)$ Copper,$(iv)$ Potassium. $(c)$ In what way is the deficiency of these nutrients harmful to crops?

Which one of the following nutrients is not available in fertilizers?

Match the column $A$ with the column $B$:

Column $A$	Column $B$
$(a)$ Catla	$(i)$ Bottom feeders
$(b)$ Rohu	$(ii)$ Surface feeders
$(c)$ Mrigal	$(iii)$ Middle-zone feeders
$(d)$ Fish farming	$(iv)$ Culture fishery

Two friends,Girish and Neeraj,were discussing Newton's third law. They were perplexed about how action and reaction are equal and opposite. They could not think of an experiment by which they could ascertain this fact. Pushkar,who was their friend,told them that he would set up an experiment to prove this to them. By performing an experiment,Pushkar demonstrated the law.
$(a)$ Can you think of an experiment by which you can demonstrate this law?
$(b)$ What values do you think Pushkar has?