We recently did a simple experiment, which happens to ________ how children's knowledge of what a hero is like determines their behaviour.

Though Jane speaks Russian well, she thinks it necessary to learn ___ foreign language.

In my opinion, he is a(n) ________ person, that is, he says what he thinks.

As a war reporter in Iraq, Shui Junyi is ____ to many dangers.

—How did she get infected?  —She _______ the viruses without any protection．