They are not a well-trained group of exercisers, _____ rather a class of participants who are mostly homeless.

答案為何填but,有but rather這個使用方法嗎?能不能填or構成or rather呢?

謝謝老師指導!

這是not A but B 結構。not...but...為關聯并列連詞,否定A,一定B。不是A,而是B,rather可有可無,用了則起強調用途。