问题
Look at these factories. I hate them. They____ many rivers here. –Yes. Something ______ to stop the pollution.
A:polluted, must do
B:had polluted , must be doing
C:have polluted , must be done
D:were polluting, must be done
B:had polluted , must be doing
C:have polluted , must be done
D:were polluting, must be done
正确答案是：
