1.Of all the economically important trees, palms have been ___.

2.Not only ___ to determine the depth of the ocean floor, but it is also used to locate oil.

3.It's high time someone ___ him to stop behaving like a child.

4.___ the English examination, I would have gone to the concert last Sunday.

5.The morning class ___ over, students rushed out of the classroom for lunch.

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