Trees are useful to man mainly in three ways, the most important of which is that they can protect ______ from droughts (干旱) and floods.
Entering the house we found him lying on the bed with his mouth _______ and eyes _______.
“Could I take your order now?” “Yes. One _____ tea and two _____ coffees.”
Mary is very clever and _____ worth teaching, but her brother is not. Look, he is now _____ asleep in class.
We were two hours late that day, which was due to the ______.
Let’s make it at seven o’clock on Tuesday morning at my office if ________.