The most likely outcome of a large increase in the amount of plants available in the area for the deer to eat is:
C. It will increase at first, but the deer will become overcrowded, causing the population to decrease.
Initially, the increased food supply can support a larger deer population, leading to growth in their numbers. However, as the population increases, competition for space and resources may lead to overcrowding, which can negatively affect the population due to factors such as limited space and increased stress, ultimately resulting in a population decline.