If man (realized) __________ the importance to protect the environment, lots of forests would not have been cut off.
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Why are you looking at me like this as if I had known it? In fact I (know) ___________ nothing about it.
The teacher ordered that all the boks (send)_________at once.
We demand that the tour guide (tell) _______ us immediatedly about any change in the schedule.
If I (not attend) ________ an important meeting yesterday, I would have come to see you.