Answer:
a. The size of their population
Explanation:
If the number of wolves increases but their food supply does not, there will be greater competition for the food.
b. is wrong. The amount of oxygen would have no effect on the competitiveness of the wolves.
c. is wrong. If the amount of food available increases, the wolves will have less need to compete for their food.
d. is wrong. If the area into which the wolves are expanding is like their current habitat, it will contain more food for them. They will have less need to compete.
