答案：B

解析：

If f(n) = n-2, then f4 = 4-2 = 2 does not equal 4, so the second condition fails. If f(n) = 2n, then f(4) = 8 not equal to 4, so the second condition fails for this function also. The other three options satisfy f(4) = 4, so it remains to check whether they satisfy the first condition.

If n = 1, and f(n) = 4, then f(2n) = f2 = 4 and 2f1 = 24 = 8, so it is not true that f(2n) = 2f(n) for all integers n. This means that the function f(n) = 4 does not satisfy the first condition. If n = 1, and f(n) = (2n)-4, then f(2n) = f2 = (22)-4 = 0 and 2f(n) = 2f1 = 2(-2) = -4, so it is not true that f(2n) = 2f(n) for all integers n. This means that the function f(n) = (2n)-4 does not satisfy the first condition.

However, if f(n) = n, then f(2n) = 2n = 2f(n), for all integers n. Also, f(4) = 4. Therefore, the function f(n) = n is the only option that satisfies both conditions.