Sunken stomata are found in the leaves of

In which of the following leaves is the palisade parenchyma absent?

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

In a monocot leaf:

Bulliform cells are present in.....

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?