Which one of the following is a xerophytic plant in which the stem is modified into the flat green and succulent structure?

Opuntia is a plant growing in dry and xeric habitats. In this, the stem having several nodes and internodes is modified into flat, fleshy, thick, green leaf-like structure called phylloclade. Phylloclade performs the function of photosynthesis like a leaf and also stores food. The leaves get modified into spines which helps to reduce transpiration.