The audience waited in________silence while their aged speaker searched among his notes for the figures he could not remember.

With Chang’e II launched successfully, China is      to send up a manned spaceship to the moon within five or six years.

She felt _____ of having asked such a silly question when the audience couldn't help laughing.

There is a wide ________of reference books to be found, so ________you look for some material needed, you can turn to me.

It is obvious that water is to be _____to the development of life.