Answer:
(C). mitosis.
Step-by-step explanation:
In multicellular organisms, mitosis is responsible for the growth, repair, and enlargement of organism, by producing more number of new identical cells. Mitosis is a type of cell division that involves formation of two similar daughter cells from a parent cell.
The Redwood tree is an eukaryotic, multicellular plant, in which growth and development occurs by the mitosis. Hence, the process that would increase the weight and size of Redwood trees is mitosis.
Thus, the correct answer is option (C).