题干

下列的曲线图分别表示有关生物学过程,对其曲线变化的描述中,正确的是(   )

A:甲图整段曲线表明,随光照强度递增,光合作用增强,呼吸作用减弱

B:乙图B点时,害虫种群抗药个体所占百分比大于A点害虫种群抗药个体所占百分比

C:生产上常用一定浓度的生长素类似物除去单子叶农作物中的双子叶杂草,丙图中曲线①表示单子叶植物

D:丁图中动物乙表示恒温动物

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B

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       If you think that running marathons will help you live a long and healthy life, new research may come as a shock. According to a recent scientific study, people who do a very strenuous workout are as likely to die as people who do no exercise at all.

       Scientists in Denmark have been studying over 1,000 joggers and non­joggers for 12 years. The death rates from the sample group indicate that people who jog at a moderate pace two or three times a week for less than two and a half hours in total are least likely to die. The best speed to jog at was found to be about 5 miles per hour. The research suggests that people who jog more than three times a week or at higher speeds of over 7 mph die at the same rate as non­joggers. The scientists think that this is because strenuous exercise causes structural changes to the heart and arteries (动脉). Over time, this can cause serious injuries.

       Peter Schnohr, a researcher in Copenhagen, said, “If your goal is to decrease risk of death and improve life expectancy, jogging a few times a week at a moderate pace is a good strategy. Anything more is not just unnecessary, and it may be harmful.”

        The implications of this are that moderate forms of exercise such as tai chi, yoga and brisk walking may be better for us than“iron man” events, triathlons and long­distance running and cycling. According to Jacob Louis Marott, another researcher involved in the study, “You don't actually have to do that much to have a good impact on your health. And perhaps you shouldn't actually do too much.”