Which of the following has the largest biomass of autotrophs in the world's oceans?

Study the diagram carefully and fill in the blanks. Choose the correct option for $A, B, C, D$ and $E$.

The carbon cycle involves which of the following sequences? (Following the logical flow)

Surface water of a lake is enriched with:

Which of the following levels is conceptual in terms of size?

$A$ farmer harvests his crop and expresses his harvest in three different ways.
$(a)$ $I$ have harvested $10$ quintals of wheat.
$(b)$ $I$ have harvested $10$ quintals of wheat today in one acre of land.
$(c)$ $I$ have harvested $10$ quintals of wheat in one acre of land,$6$ months after sowing.
Do the above statements mean one and the same thing? If your answer is yes,give reasons. If your answer is 'no',explain the meaning of each expression.