The competitive effect of one species on another (interspecific competition) is related to…
a. how strongly each competitor can obtain and retain the limiting resource
b. the population density of the competitors
c. the degree of niche overlap
d. all of the above
e. none of the above

d)All of the above

Explanation: Competitive effect is defined as the interaction created between species or organism , which usually results in negative situation. There are certain condition for the competition such as  supply of any resource in limited quantity, etc.So competition is also invoked by the density of the species present and in order to exist  in an ecosystem and thus there is the high chances of the overlapping of species as well.

Therefore,option(d) is the correct option.

thinking it would be d not too sure but i think it's right