At the beginning of this century, medical scientists made an interesting discovery: we are built not just of flesh(肌肉) and blood but also of time. They were   21  to show that we all have a ‘body clock’   22  us, which controls the   23  and fall of our body energies,   24  us different from one day to the next.
The   25  of a ‘body clock’ should not be too   26  since the lives of most living things are controlled   27  the 24-hour night-and-day cycle(循环). We feel   28  and fall asleep at night and become  29  and energetic during the day. If the 24-hour cycle is   30  most people experience unpleasant   31 . For example, people who are not   32  to working at night can find that   33  of sleep causes them to   34  badly at work.
  35  the daily cycle of sleeping and   36 , we also have other cycles which   37  longer than one day. Most of us would   38  that we feel good on some days and not so good on  39 ; sometimes our ideas seem to flow and at other times, they   40  do not exist.
  

A．anxious B．careful C．able D．proud

A．around B．inside C．between D．on

A．rise B．supply C．use D．movement

A．showing B．treating C．changing D．making

A．idea B．opinion C．story D．invention

A．difficult B．exciting C．interesting D．surprising

A．from B．over C．by D．during

A．dull B．dreamy C．tired D．peaceful

A．regular B．excited C．clear D．lively

A．shortened B．disturbed C．reset D．troubled

A．moments B．senses C．feelings D．effects

A．used B．allowed C．expected D．prevented

A．miss B．none C．need D．lack

A．show B．perform C．manage D．control

A．With B．Except C．As well as D．Rather than

A．waking B．moving C．living D．working

A．repeat B．remain C．happen D．last

A．believe B．agree C．realize D．allow

A．others B．the other C．all other D．other

A．only B．just C．still D．yet