Many ____ have developed as people have found ___how to sing in diffferent ways

问题描述:

Many ____ have developed as people have found ___how to sing in diffferent ways
A:music B:musics C:kind of music D:kinds of music
A:out B:over C:off d:through

D,A
music不可数所以不能直接跟many.而many修饰的必然是可数的复数形式,因此是kinds而不是kind.
find out是个固定搭配的词组