Correct Option: B

Maximum harm to a tree is caused by loss of leaves. This means that the tree will loose its ability to perform photosynthesis or food manufacture. Leaves are a plant’s main photosynthetic organs. Leaf structure is closely associated with its photosynthetic function. Leaves must permit carbon dioxide access to the photosynthetic cells but impede water from diffusing out. The oxygen that is a waste product of photosynthesis must be allowed to escape from the leaf.