영어 괄호 넣기 문제 답이 궁금해요

다음 문장에서 (ⓐ)에 들어갈 표현이 무엇인지 궁금합니다.
“For knowledge of the external world, whether of things or of people, we continually come back to our five senses in the end. (ⓐ), if a great mass of data relevant to social science is sensory, we have also to admit an important collection that is not — namely the whole body of primary mental or psychological experience.”
보기는 for example, in other words, furthermore, nevertheless입니다.