What Do Both the C₄ and CAM Pathways of Photosynthesis

What do both the C₄ and CAM pathways of photosynthesis allow plants to do?

A) to perform photosynthesis in the absence of carbon dioxide
B) to outcompete C₃ plants in cool, dry conditions
C) to keep stomata partially or completely closed during the hottest parts of the day
D) to take up carbon dioxide at night and then store it as an acid until the day