As the pace of life continues to

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. 1______ being on the go is essential for a healthy mind and body.
Stress is a natural part of everyday life and there is no 2______ to avoid it. In fact, it is not the bad thing as it is often 3 ______ to be. A certain amount of stress is vital to provide motivation and give purpose to life. It is only 4______ the stress gets out of 5______ that it can lead to poor performance and ill health.
The amount of stress a person 6______ withstand depends very much on the individual.Some people are not 7______ stress and such strong characters are obviously prime material for managerial responsibilities. Others 8______ at the first sight of unusual difficulties. When 9______ to stress, in whatever form, we react both chemically and physically. 10______ we make choice between "flight or fight"and 11______ more primitive days the choices might make the difference between life and death. The crises we meet today are 12______ to be so extreme, but however little the stress, it involves the same response. It is when such a reaction lasts long, 13______ continued exposure to stress, that health becomes 14______ Such serious conditions as high blood pressure and heart diseases have 15______ links with stress Since we cannot remove stress from our lives, we need to find ways to deal with it.
13
A、in
B、under
C、by
D、about
【正确答案】：B
【题目解析】：译文：就是当这种反应持续很长时间时，在持续性的压力下，健康会遭遇危险。此处用介词under合适，表示“在...的情况下”。答案为B。