The best answer is B.
Mosses grow close to the ground because they have no vascular tissue or system. A vascular system in plants can simply be described as a series of tubes that can transport water and nutrients over a distance from one part of the plant to another. Because of this, mosses unlike other plants such as trees must be close to the water source on the ground to be able to take up water and nutrients.
Trees have a vascular system which enables them to transport water and nutrients over a large distance and can thus afford to grow tall sometimes over 100 ft tall like the redwood and sequoia trees.
