I think you are confused to think that only people on the committee can have financial interest in this. All people could have interest in this because it does not specify that they don't. For a must be true its really important to not assume anything that is not explicitly stated.

B is wrong because there could be some people who are not on the committee who could have financial interest in this decision. There is nothing said about the people not on the committee so we cant assume that none of them have a financial interest. There are people who live in the suburbs, so it is possible that at least 1 person in the suburbs has financial interest therefore B is not always true.

E must be true because there is guaranteed to be at least one person with financial interest who does not live in the suburbs. There is at least one person one the committee with these interests and that person is guaranteed to not live in the suburbs.

Its important to remember people on the planning committee are within the group of all people. There are some people on the committee who have financial interest, and none of those people live in the suburbs. Therefore those people must live somewhere other than the suburbs. Therefore there must be some people who live outside of the suburbs with financial interest which leads to E.

LMK if that makes sense first time trying to explain a problem