The correct option is B Both statements are correct
Crassulacean acid metabolism is a mechanism of photosynthesis involving double fixation of CO2 which occurs in succulents belonging to Crassulaceae, Cacti, Euphorbias and some other plants of dry habitats. Here, the stomata remains closed during the daytime and opens only at night, e.g Sedum,Kalanchoe,Opuntia. Sunken stomata are deep seated stomata in which subsidiary cells lie above the guard cells. So, the correct answer is 'Both statements are correct'.