It has come to my attention that our country's planning commission is wedded to the concept of nodal development in our rural towns. This concept is problematic for several reasons. First, to succeed, nodes must have a critical mass of inhabitants. Studies suggest that 2,500 is the smallest possible group required to support retail businesses within a node. Our rural nodes would have far fewer residents -- at most 1,500.
Its very clear it should be D as none of the other terminologies ( conclusion, assumption ) confirm to the bold sentence
In the preceding argument, the portion in boldface plays which of the following roles?
(A) It is a conclusion that must be proven in order for the argument to be valid.
(B) It is an assumption that provides little support for the argument's conclusion.
(C) It is a premise that has little validity in the context of the argument.
(D) It provides specific evidence to support the writer's premise.
(E) It provides specific evidence to counter the writer's premise.