The correct option is
D Euphorbia tirucalliIn certain plants, the stem is modified to perform photosynthesis. Cladode is a form of modified stem, which is green and fleshy in nature. The leaves are modified to form spines. The cladode arises from the axil of these leaves. There are many examples of plants in which there are stem modified to form cladode like
Euphorbia tirucalli and
Euphorbia antiquorum. There are many cylindrical cladodes in this plant. The cladodes are succulent and there are small leaves.
Thus, the correct answer is option D.