“Body clocks” are biological methods of controlling body activities. Every living thing has one. In humans, a body clock controls normal periods of sleeping and waking. It controls the times when you are most likely to feel pain. Eating, sleeping and exercising at about the same time each day will help keep body activities normal. But changes in your life—a new job, for example—destroy the balance and thus cause health problems. You could have difficult sleeping, for example. Scientists suggest that early afternoon is the best time of day for physical exercise. They say we are stronger and faster then. Later, about four o'clock, most people feel tired because of the drop of sugar level in the blood. Early afternoon also is a good time to do tasks about memory（记忆） and mathematics. If you must study, however, do it just before going to sleep at night. Scientists say you are more likely to remember information when there is a short delay（耽搁）between study and bed. Body clocks control all the activities from day to day. They also produce changes about every ninety minutes during the day. At the end of such a time period, our ability to think hard begins to become weak. That is the time we are most likely to day-dream. Within fifteen minutes, we are ready to go back to what we were doing.

根据课文默写。
① 迢迢牵牛星，                        。     （《古诗十九首》）
② 抽刀断水水更流，                        。 （李白《宣州谢眺楼饯别校书叔云》）
③                       ；思而不学则殆。      （《论语》八则）
④ 吴楚东南坼，                       。      （杜甫《登岳阳楼》）
⑤                         ，带月荷锄归。      （陶渊明《归园田居》）
⑥ 浊酒一杯家万里，                       。  （范仲淹《渔家傲》）
⑦ 山重水复疑无路，                       。  （陆游《游山西村》）
⑧                           ，听取蛙声一片。  （辛弃疾《西江月 夜行黄沙道中》）
⑨伤心秦汉经行处，                         。 （张养浩《山坡羊 潼关怀古》）
⑩                     ，灵旗空际看。         （夏完淳《别云间》）

使用电火花计时器在纸带上打点时，合理的操作顺序应该是（   ）