If It Is in Our Power to Prevent Something Bad

If it is in our power to prevent something bad from happening, according to Singer, then . . .

A) We should do it regardless of any other considerations.
B) If we can do it without thereby sacrificing anything of comparable moral importance, we should.
C) It would be good for us to do it but not wrong for us not to do it.
D) We should only do it if it means we don't have to give up our current way of life.