WHEN I WAS YOUNG, THE RIVERS _____ CLEANER THAN THEY ARE NOW.A. USE...

20.When I was young, the rivers _____ cleaner than they are now.A. use to beingB. used to beC. used to beingD. use to beChọn phương án (A hoặc B, C, D) ứng với từ/cụm từ có gạch chân cần phải sửa: