Luci, you are missing a nuance in the meaning of the sentence that is difficult even for a native speaker of English to identify. An individual would not be the former chair of a planning board for 18 consecutive years; instead, the sentence is attempting to say that Joan was actully the chair of the planning board for 18 consecutive years and that she attended these meetings during those 18 years. Thus, choices A, B, and C and be eliminated. As D is a run on sentence, E is the best answer.