—I find it quite hard to understand this passage.—Really? _____ there are few new words in it.
--- Lily is ill in hospital .---Really ? I _____ know she was ill .
The task is so hard fore . I don’t know _______________.
Good books help us ___________ a whole new world to me .
There is no air _______ water on the moon .
They don’t know what ___________ the problem .