语法与词汇
After people have learned that magnets attract things, centuries passed _____ they took note of the fact thatmagnets sometimes also repel things.
【正确答案】
A
【答案解析】句意：在人们了解到磁铁会吸引物质的几个世纪之后，他们才注意到磁铁有时也排斥物质。before应该理解成“几百年过去了，人们才……”。如果用after应该改为“after centuries passed they took note of the fact”。如果用until，应该是“they didn’t take note of the fact that...until centuries passed”。因此，本题的正确答案为A。