Bulliform cells are the modification of

The correct situation of mesophyll in an isobilateral grass leaf is shown by:

Many types of grass leaves have the ability to roll or unroll because they .....

The stomata in an isobilateral leaf:

The epidermis in a dorsiventral leaf:
$(a)$ Covers both adaxial and abaxial surfaces
$(b)$ Is not covered by cuticle
$(c)$ Bears more stomata on the upper side
$(d)$ May even lack stomata on the upper side
Which of the above statements are correct?

Bulliform cells are responsible for