Young as he is, David has gained ____ rich experience in ____ society.
We need to get to the root of the problem______ we can solve it.
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.