At the beginning of this century, medical scientists made an interesting discovery; we are built not just of flesh and blood but also of   36 . They were able to show that we all have “a body clock”   37    us, which controls the   38   and fall of our body energies,   39   us different from one day to the next.

The   40   of “a body clock” should not be too   41   since the lives of most living things are controlled   42   the 24 hour night-and-day cycle. We feel   43   and fall asleep at night and become   44   and energetic during the day. If the 24 hour-cycle is   45   , most people experience unpleasant   46   . For example, people who are not   47   to working at night can find that   48   of sleep causes them to   49   badly at work.

  50   the daily cycle of sleeping and   51  , we also have other cycles which   52   longer than one day. Most of us would   53   that we feel good on some days and not so good on    54   ; sometimes our ideas seem to flow and at other times, they   55   do not exist.

In order not to be disturbed, I spent three hours _______ in my study.

   A. locking          B. locked           C. to lock       D. to be locked

 It was a pity that the great writer died________ his works unfinished.

    A. for             B. with             C. from         D. of

I don’t doubt           our team will win the 4×100一meter race．

    A．when         B．whether         C．that        D．which

--- Can I look at the menu for a few more minutes before I decide?

   ---- Of course._______ sir.

   A. Make yourself at home              B. Enjoy yourself

   C. Take your time                     D. It doesn't matter

Some medicine，when wrongly           ，can kill a person

    A．taken          B．taking          C．take        D．to take

---You were tired after the 10,000一 meter race．weren’t you?

   --- Yes,           I was out of breath．

    A．not at all      B．not a little       C．not really     D．not a bit

 After three months, these young students finally became used to the ______ of life in a big

   city abroad.

   A. speed            B. pace                     C. rate                    D. frequency 

Years ago we didn’t know this, but recent science _____ that people who don’t

   sleep well soon get ill.

   A. showed         B. has shown        C. will show           D. is showing

Most animals have little connection with___ animals of ___ different kind unless they kill  

    them for food.

   A. the ; a          B. × ; the          C.   ×; a        D. the ; the