The correct option is
C Both A and B
A culm is the areal jointed stem (above ground) of grass or bamboo. Typically, the culms are hollow but some species of bamboo have solid culms. In members of Poaceae family, the stem is underground rhizome in all perennial grasses,
cylindrical, culm with conspicuous nodes and internodes, internodes hollow, herbaceous or woody, glabrous or glaucous, vegetative shoots are arising from the base of aerial stem or from underground stems.So, the correct answer is 'Both A and B'.