16¡¢Granite crystals are large enough to be seen with the (naked) eye.

A.wary

B.candid

C.unaided

D.discerning

17¡¢Having (enlisted) in the Marine Corps in August 1918, Opha May Jonnson was made a provisional sergeant a month later.

A.considered

B.joined

C.written to

D.Risen in

18¡¢The (widespread)use of Xª²rays for diagnostic purposes poses the risk of overexposure to radiation.

A.medical

B.spacious

C.experimental

D.General

19¡¢The geysers, one of the most unusual phenomena in nature, is beautiful to (behold).

A.view

B Relate

C.Sketch

D.Withhold

20¡¢The lymphatic system includes a network of tiny capillaries that lie (adjacent )to the fine blood vessels.

A.independent of

B.obscured by

C.near

D.within

A.the greater the alpha waves will be.

B.the slower the brain waves will appear.

C.activity pattern of the brain.

D.the closer one is to the initial Stage 1 sleep .

22¡¢(ͬ21Ìâ)Before one reaches the deepest sleep,_____

A.muscular inhibition occurs .
B.one¡¯s body muscles b***me paralyzed.

C.loss of consciousness has already occurred.

D.one¡¯s eyes begin to move as if looking at something.

23¡¢(ͬ21Ìâ)REM sleep is characterized by____

A.a drop in temperature.

B.a loss of consciousness.

C.a lack of body movement.

D.the appearance of data waves.

24¡¢(ͬ21Ìâ)Muscular relaxation, a temperature drop, and breath regularity are characteristics of____

A.REM sleep.

B.Stage 1 sleep.

C.delta rhythms.

D.Stage 2 and 3 sleep.