According to the text,which of the following predictions of a community structured by interspecific competition has not been tested using the null model analysis approach?

A) Potential competitors coexisting in a community should have differentiated niches
B) Potential competitors in a community with little or no niche differentiation should have negatively associated distributions
C) Potential competitors who coexist do so often due to morphological differentiation of their niches
D) Answers a, b, and c