Statement (1) is sufficient. Given the ratio of the 9 removed socks, we can calculate the exact number of each color socks removed--6 blacks and 3 whites. That leaves us with 12 whites, so the answer is "yes."

Statement (2) is also sufficient. Call the number of white socks removed w, which means that the number of black socks removed is 9 - w. Since we started with 15 white socks, the number of remaining white socks is 15 - w; the number of remaining black socks is 10 - (9 - w) = 1 + w.

Given the ratio after removal, we can set those expressions equal to the ratio:
white/black = 3/1
(15 - w)/(1 + w) = 3/1
15 - w = 3(1 + w)
15 - w = 3 + 3w
12 = 4w
w = 3

Recall that w represents the number of white socks removed. If 3 socks were removed, 12 white socks remain, so the answer is "yes." Choice (D) is correct.