Answer:
B. Competition for light and moisture
Explanation:
Plants grow towards sunlight which is necessary for photosynthesis, of which they utilize sunlight, carbondioxide, and moisture to manufacture their food. In the tropical rain forest, competition is intense among plants for sunlight and moisture.
The trees/plants that are able to get enough sunlight and moisture gain advantage over others as they grow bigger and taller, as the rest struggle to get some sunlight and moisture. The canopy of taller trees usually cut-off sunlight from teaching shorter trees, thereby making availability of sunlight to the shorter trees quite limited. As a result of this, we have variations of trees with different height in the tropical rainforest.
