电刷用铜和石墨粉压制而成，以减小电刷（）及增加耐磨性。

Directions: Complete the following passage by using the words in the box. Each word can only be used once.   Note that there is one word more than you need.

A. essential	B. endangered	C. going	D. performance	E. crises
F. supposed	G. consequence	H. material	I. exposed	J. involves

As the pace of life continues to increase, we are fast losing the art of relaxation. Once you are in the habit of rushing through life, being on the   小题1:  from morning till night, it is hard to slow down. But relaxation is   小题2:  for a healthy mind and body.
Stress is a natural part of everyday life and there is no way to avoid it. In fact, it is not the bad thing as is often   小题3:  to be. A certain amount of stress is vital to provide motivation and give purpose to life. It is only when the stress gets out of control that it can lead to poor   小题4: and ill health.
The amount of stress a person can stand depends very much on the individual. Some people are not afraid of stress, and such characters are obviously prime   小题5:  for managerial responsibilities; others lose heart at the first sign of unusual difficulties. When   小题6:  to stress, in whatever form, we react both chemically and physically. In fact we make choice between “flight or fight” and in more primitive (远古的) days the choices made the difference between life or death. The   小题7:  we meet today are unlikely to be so extreme, but however little the stress, it   小题8:  the same response. It is when such a reaction lasts long, through continued exposure to stress, that health becomes   小题9: . Since we can’t remove stress from our lives (it would be unwise to do so even if we could), we need to find ways to deal with it.