It is well known to us all that a lot of rivers _______by factories.
#102816
A
are polluting
B
have been polluting
C
are being polluting
D
are being polluted
推荐题目
The manager was concerned to hear that two of his trusted workers ______. 
#102158
A
will leave
B
are leaving
C
have left
D
were leaving
When the old man ______ to walk back to his house, the sun       itself behind the mountain. 
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A
started; had already hidden
B
had started ;had already hidden
C
had started; was hiding
D
was starting; hid