A) If two competing species coexist in a stable environment, then they do so as a result of niche complementarity. B) If two competing species coexist in a stable environment, then they do so as a result of niche differentiation. C) If two competing species coexist in an unstable environment, then they do so as a result of niche complementarity. D) If two competing species coexist in an unstable environment, then they do so as a result of niche differentiation.