Which characteristic of living organisms ensures that the population of each species remains limited?

Which of the following is a characteristic property of a living organism?

Assertion: The number of cells in a multicellular organism is inversely proportional to the size of the body.
Reason: All cells of the biological world are alive.

The unique phenomena of life in living organisms are the result of interactions within their bodies. Explain.

What is the science that deals with the study of plants from various perspectives called?

Match Column-$I$ (Scale) with Column-$II$ (Biological entity) and select the correct option:
| Column-$I$ (Scale) | Column-$II$ (Biological entity) |
| :--- | :--- |
| $(a)$ Macroscopic | $(i)$ Cells |
| $(b)$ Microscopic | (ii) Organisms |
| $(c)$ Sub-microscopic | (iii) Society |
| $(d)$ Conceptual | (iv) Atoms |