Don't use water to put out the fire if oil catches fire. As is known, oil ________ float on water.
If you have any doubts about your health, you’d better______ your doctor at once.
Tom had tothe invitation to the party last weekend because he was too busy.
Despite the previous rounds of talks, no agreement______ so far by the two sides.
______ for two days, Steve managed to finish his report on schedule.
I ______ have worried before I came to the new school, for my classmates here are very friendly to me.