The most likely outcome of a large increase in the amount of plants available for white-tailed deer in the ecosystem is:
D. It will increase at first, but the deer will become overcrowded, causing the population to decrease.
Initially, the increased availability of food (plants) will likely lead to an increase in the deer population as more resources support higher numbers. However, as the population grows, the deer may eventually face competition for space and other resources, leading to overcrowding. This can result in increased stress on the population, potential food shortages, and ultimately, a decrease in population size as the carrying capacity of the ecosystem is exceeded.