这句话是强调句还是定语从句呢?
It was my sister that/who helped me out when I was in trouble.
去掉IT be that句子也成立,可是若是定语从句,my sister带入也成立
是强调句,去掉It was...that/who便是:My sister helped me out when I was in trouble.我有困难时,我姐姐帮了我。语句通顺。
理解为定语从句非常牵强,汉语意思不非常通顺:那是我有困难的时候帮助了我的我的姐姐。