For Natural Selection to Occur, There Must Be Some Competition

For natural selection to occur, there must be some competition for resources, survival, or reproduction. Why is this so?

A) The struggle of competition makes individuals stronger.
B) Populations evolve to preserve the species and don't change unless they must.
C) Without competition, there is no pressure to mutate.
D) If all individuals pass on their genes equally, the proportion of the various alleles will remain the same.