The correct option is C Phylloclade
A phylloclade is a flattened stem with multiple internodes and nodes that serve as a leaf. It arise in the axil of the leaf, does not have any axillary bud but shows unlimited growth. The spines on its surface represent the modified leaves of the axillary bud which serve to check the rate of transpiration and also protect the plant from herbivores. In Opuntia, leaves are reduced to spines and stem is modified to perform photosynthesis.
Thus, the correct answer is option B.