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 Xrays 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、(同21題)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、(同21題)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、(同21題)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.