which 指的是a pronunciation exercise
遇到从句可以把句子分成两句独立的话来理
第一句是the teacher asked us to do...
第二句是he (the teacher) would say a word or two in French（用法语说1,2句话）in a pronunciation exercise
注意 第二句话里就有了in
因为which 只指a pronunciation exercise,因此需要添上in