Which choice best maintains the sentence’s focus and clarity?

This option focuses solely on animals and their actions, omitting the critical inclusion of people. As a result, it does not fully represent the scope of the phenomenon and lacks clarity about the shared involvement of both animals and people in the 'vacancy chain.'

This choice inaccurately shifts the focus to economists as the primary subjects illustrating the phenomenon, which undermines the intended focus on animals and the collective involvement of people. It also suggests that animals are merely subjects of study rather than active participants in the phenomenon.

This option is confusingly worded and implies that animals illustrate economists, which distorts the relationship between the subjects and the phenomenon. It fails to maintain clarity and focus on the actual point being made about the 'vacancy chain' involving both animals and people.