Answer:
D is the correct choice.
Explanation:
30^2 = 900, which is less than 2000 and thus too small. Reject choice A.
35^2 = 1225, which is less than 2000 and thus too small. Reject choice B.
40^2 = 1600, less than 2000. Reject choice C.
45^2 = 2025, which is greater than 2000 but less than 2500. This is the correct choice. D is correct.