The size of vascular bundles in a dorsiventral leaf is dependent on

During water stress,the bulliform cells:
$(a)$ Become turgid
$(b)$ Become flaccid
$(c)$ Make the leaves curl inwards
$(d)$ Make the leaf surface exposed
The correct options are:

Assertion: Bulliform cells are useful in the unrolling of leaf.
Reason: Bulliform cells store water.

In leaves,the protoxylem elements:

The vertical section of a dorsoventral leaf through the lamina shows three main parts namely,epidermis,$A$,and vascular system. The epidermis,which covers the upper surface is $B$ and the lower surface is covered by $C$ of the leaf. Choose the correct combination of $A$,$B$,and $C$.

Bulliform cells are found in: