单项选择题

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 go from morning till night, it is hard to slow down. (16) relaxation is essential for a healthy mind and body.
Stress is a natural part of everyday life and there is no (17) to avoid it. In fact, it is not the bad thing as it is often (18) to be. A certain amount of stress is vital to provide motivation and give purpose to life. It is only (19) the stress gets out of (20) that it can lead to poor performance and ill health.
The amount of stress a person (21) withstand depends very much on the individual. Some people are not (22) stress, and such characters are obviously prime material for managerial responsibilities. Others (23) at the first signs of unusual difficulties. When (24) to stress, in whatever form, we react both chemically and physically. (25) we make choice between "flight or fight" and (26) more primitive days the choice made the difference between life and death. The crises we meet today are (27) to be so extreme, but however little the stress, it involves the same response. It is when such a reaction lasts long, (28) continued exposure to stress, that health become (29) . Such serious conditions as high blood pressure and heart diseases have (30) links wit stress. Since we cannot remove stress from our lives, we need to find ways to deal with it.

30（）

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