The black ______ in the United States before the Civil War.

A.looked on as

B.were looked on as

C.were looked down upon as

D.were looked down upon

答案及解析： D

解析：

本题B、C两项易被误选，由于空格后没有名词，即不表明“被看作什么”，故不应有介词as。D项意为“被轻视”。