单选题 Our bodies are wonderfully skilful at maintaining balance. When the temperature jumps, we sweat to cool down. When our blood pressure falls, our hearts pound to compensate. As it turned out, though, our natural state is not a steady one. Researchers are finding that everything from blood pressure to brain function varies rhythmically with the cycles of sun, moon and seasons. And their insights are yielding new strategies for keeping sway such common killers as heart disease and cancer. Only one doctor in 20 has a good knowledge of the growing field of "chronotherapeutics (历时治疗术)", the strategic use of time (chronos) in medicine. But according to a new American Medical Association poll, three out of four are eager to change that. "The field is exploding," says Michael Smolensky. "Doctors used to look at us like "What spaceship did you guys get off?" Now they"re thirsty to know more."
In medical school, most doctors learn that people with chronic conditions should take their medicine at steady rates. "It"s a terrible way to treat disease," says Dr. Richard Martin. For example, asthmatics (气喘患者) are most likely to suffer during the night. Yet most patients strive to keep a constant level of medicine in their blood day and night, whether by breathing in on an inhaler (吸器) four times a day or taking a pill each morning and evening. In recent studies, researchers have found that a large mid-afternoon dose of a bronchodilator (支所管张剂) can be as safe as several small doses, and better for preventing nighttime attacks.
If the night belongs to asthma, the dawn belongs to high blood pressure and heart disease. Heart attacks are twice as common at 9 a.m. as at 11 p.m. Part of the reason is that our blood pressure falls predictably at night, then peaks as we start to work for the day. "Doctors know that," says Dr. Henry Black of Chicago Medical Center, "but until now, we haven"t been able to do anything about it." Most blood pressure drugs provide 18 to 20 hours of relief. But because they"re taken in the morning, they"re least effective when most needed. "You take your pill at 7 and it"s working by 9," says Dr. William White of the University of Connecticut Health Center, "but by that time you"ve gone through the worst four hours of the day with no protection." Bedtime dosing would prevent that lapse, but it would also push blood pressure to dangerously low levels during the night.

【正确答案】 A

【答案解析】[解析] 此题答案见短文的第一段。作者开篇便提到：Our bodies are wonderfully skilful at maintaining balance.(我们的身体有非常奇妙的平衡机制。)随后作者又说：“当我们体温升高，便会通过出汗降温；当血压下降，心脏跳动便会补充血液”，从而排除了选项B和C。可见：everything from blood pressure to brain function varies rhythmically with the cycles of sun, moon and seasons(从血压到大脑功能一切情况都会随着太阳、月亮和季节的循环而发生规律性的变化)，即人体在维持平衡方面靠自然条件的变化来调整自身。故选项A正确。