CAM plants perform photosynthesis during the day even though their stomata are closed. How do these plants obtain carbon dioxide in order to carry out photosynthesis?

A) CAM plants use glucose as their main source of carbon dioxide during periods of drought.
B) CAM plants transport carbon dioxide from the soil through the phloem to offset the loss of carbon dioxide uptake in the leaves.
C) Carbon dioxide is stored within specialized bundle sheath cells during mild temperatures for use during drought.
D) CAM plants open their stomata at night to obtain carbon dioxide.