Now that there are only a few minutes left, we’d better talk about the plan in _____.

There might be life on other planets, but so far scientists haven't found enough ________ to prove it.

. It is clear that the whole world is passing through a social revolution in which a central _____ must be taken by scientists and technologists.

The system has been designed to give students quick and easy_____to the digital resources of the library.

Do you know the        of the saying I just quoted?