In CAM Plants, Such as Cacti

In CAM plants, such as cacti,

A) the stomata are open both day and night.
B) the stomata are open during the day to let in carbon dioxide even though they cannot afford to lose the water.
C) stomata are absent because water loss through them is too great.
D) stomata open at night.
E) guard cells are present but operate the reverse of the guard cells of non-CAM plants.