Answer: Option 'B' is correct.
Step-by-step explanation:
A temperate deciduous forest is dominated by oak trees, which produce acorns. Populations of deer, black bear, and squirrels all rely on the acorns as a primary source of food. A large portion of the forest is cut down, causing it to lose most of its oak trees.
Since we have given that populations of deer, black bear and squirrels have dependent upon acorns as their primary source of food.
After cutting down most of the oak trees, all these populations would not get their primary food enough like before which results in deer get less likely to survive as neither of the population gets enough primary food for their survival.
Deer would reproduce less ,so, their population would decline.
Hence, option 'B' is correct.