高中英语改错题，求助大神There was a time when even our physics teacher c

高中英语改错题，求助大神There was a time when even our physics teacher can't understand science
1:There was a time when even our physics teacher can't understand science-----but not anymore!
2:That's a tricky question.I can't answer it for you.but before I do,I need to think about another question.