The two girls are so alike that strangers find_____ difficult to tell one from the other.
Vegetables _________ many kinds of vitamins and many other useful materials. We should eat them_________.
__________ is important to a person is ___________ he must know _________ he is fit for.
Supermarkets are supplied with __________ red lucky gifts at the Spring Festival.
I thought my eyes must be playing tricks _______ me.
In the quiet darkness, I could hear someone _______ the door and go upstairs.