_______(48)A.The ray penetrated every one of them
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_______(48)
A.The ray penetrated every one of them except the key
B.She was very surprised by this request
C.how then could any ray penetrate
D.It was a great invention
E.Other uses came later
F. Doctors quickly saw how this could be used
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答案:B
该句中this request指代前一句“He called his wife into the laboratory and asked her to hold her hand between the lamp and a photographic plate."
