单项选择题

A laser can be best described by______.

A．a device for stimulating atoms and molecules to emit light
B．an atom in a high energy state
C．a technique for destroying atom or molecules
D．an instrument for measuring light waves

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热门试题

单项选择题

Townes's early work with stimulate emission was done with microwaves because______.

A．he was not concerned with amplification
B．his partner Schawlow had already begun work on the laser
C．it was easier to work with longer wavelengths
D．the laser had already been developed

单项选择题

The author suggests that______.

A．poetry tends to make the reader disappointed
B．poetry makes its readers sentimental
C．poetry is more important than words
D．poetry often captures real human feelings