根据材料请回答 31～35 题
How to Extend Your Life
We all age at different rates.Heredity(遗传)clearly plays an important part.But re-cent research studies by gerontologists (研究老年医学的专家) indicate that life-style. may be equally significant in determining who will remain youthful.
As a rule, single men and women have shorter lives than married ones.Studies shove that those who have been widowed(寡居的), especially men, have a longer life expectancy(平均寿命)if they remarry soon.Both men and women seem to have a greater resistance to disease and death when their marriage is undamaged.According to a 1960 study, women who have borne three children have the lowest mortality rates(死亡率).Those who have borne four or more have the highest.Childless women and those with only one child gen-erally do not live as long as mother of two or three, according to University of Chicago so-ciologists Evenly M.Kitagawa and Philip M.Hauser.
Sleep also affects the aging rates significantly.It is impossible to say how much sleep is ideal.Some people seep five hours a night; others seem to require eight or nine.Scien-tists agree that consistency(一致性)in sleeping pattern is more significant; it is better to get six hours； sleep every night than ten hours one night and three the next.
While it is true that very few people who enjoy a long life are fat, this does not mean that every pound you gain is going to shorten your life.In fact, an ongoing study in Fram-ingham, Mass, has shown that during at least 30 years of middle life, leanness(消瘦)was a higher factor for mortality than fatness.What is known is that weight extremes(极端)in either direction are definitely unhealthy.Weighing 20 percent more or less than you should weigh can, in certain case, be a life shortener.
The benefits of regular exercise are indisputable(无可争辩的).Men engaged in ener-getic and persistent physical labor have fewer heart attacks.But many researchers believe that exercise need not be very strong to keep you in shape, The first principle of any life-extension program, then, is to enjoy every moment of the life you have- whether it lasts one more year or a hundred.As the philosopher Jean Jacques Rousseau put it: "Teach him to live rather than to avoid death.Life is not breath but action, the use of our senses, mind, faculties, and every part of us which makes us conscious of our being."
第 31 题 Which of the following is NOT beneficial to the lengthening of life？

A. You should keep a good sleep habit.
B. You should do physical exercises on a regular basis.
C. You should try and remain neither too lean nor too fat.
D. You should take part in a guided life-extension program.