Usually a child's behavior is a ________ of his family environment. 

There is no _____ that taking regular physical exercise is good for your heart.

The author had qualified as a doctor but later gave up the _____ of medicine for full-time writing.

The writer was always looking for suitable _____ to use in his next story.

It can’t be a（n） _______ that four jewelry stores were robbed in one night．