If the deer population increases, they will consume more grass, leading to a decrease in the plant population. The most likely consequences from the options given are:
- The plant population would decrease.
- The lion population would decrease. (This could occur eventually if the deer population is sustainable, but if deer numbers rise too high, food scarcity can lead to population decline.)
However, if we focus on immediate consequences, the correct response is:
- The plant population would decrease.