D) option is correct
Step-by-step explanation:
Null model of community structure describes the communities which occur in the absence of a mechanism
Fundamental niche represents all the environmental conditions where a species is able to live or can live, there are no ecological barriers present in this type of niche
Species interactions modify the fundamental niche as a result distribution and abundance of species changes, ecological barriers comes into existence and fundamental niche changes into realized niche where species actually lives