The Dolly Varden char is found at higher altitudes than another fish species,the white-spotted char.One reason this occurs is because

A) Dolly Varden char cannot occupy the habitat where white-spotted char live even when there are no white-spotted char there.
B) Dolly Varden char could outcompete white-spotted char and they actually are found in lower altitude zones where white-spotted char live.
C) The boundary is due to temperature-mediated competition that favors white-spotted char.
D) The boundary is due to behavioral and morphological-mediated competition that favors white-spotted char.