【单选题】X 射线是由德国物理学家伦琴于1895年发现的,它是高速电子在真空环境中撞击阳极靶而产生的,一般靶面由( )制成。
【单选题】Why does the speaker tell the story about Newton?
A.
To illustrate what a great scientist he was.
B.
To explain why lab equipment must be cleaned carefully.
C.
To emphasize the need for proper precautions.
D.
To show how theoretical chemistry has advanced.
【单选题】If you feel ______ you should listen to some light music to relax yourself. [ ]
【单选题】德国物理学家伦琴于( )年发现了 X 射线,由此产生了放射诊断学,开创了医学影像诊断的先河。
【单选题】If you feel ______,you should listen to some light music to relax yourself.