The usual shape of a growth curve is:

Growth is maximum in the zone of

Assertion $(S)$: Growth occurs when anabolic processes exceed catabolic processes.
Reason $(R)$: Growth is the result of metabolism.
$(A)$ Both $S$ and $R$ are true,and $R$ is the correct explanation of $S$.
$(B)$ Both $S$ and $R$ are true,but $R$ is not the correct explanation of $S$.
$(C)$ $S$ is true and $R$ is false.
$(D)$ $S$ is false and $R$ is true.

Exponential growth in plants can be expressed as

Water is required in plant growth for

Maximum elongation takes place in