Answer:
C. It prevents water loss
A. It carries out photosynthesis
Step-by-step explanation:
Cactus is a xerophytic plant i.e. it can survive in an environment with no or little amount of water. To do this, cactus plant possess certain adaptational features that allow it to be successful in a xerophytic environment.
One of these features is its reduction of leaves to spines in order to reduce the loss of water via transpiration. In respect to this, the swollen stem of the cactus plant called CLADODE performs the process of PHOTOSYNTHESIS in lieu of its absent leaves.
Also, the stem has a thick waxy coat as stated in this question in order to prevent the loss of water.