Answer:
B.The number of cactus plants would increase
Explanation:The number of cactus plants will increase because if the kangaroo rats were killed off then the cactus plants will not have anything eating them because the kangaroo rats were killed.
This also affects the whole food chain because the number of snakes will decrease because the kangaroo rats is what the snakes ate, and with the snakes decreasing then so would the foxes because the snakes are what they ate so there wouldn't be as much of them.