单项选择题

The reason why the laser beam is very strong is that ______.

A．it is artificially illuminated (照亮)
B．it is made up of a concentrated beam of light
C．it sends out heat in all directions
D．its heat is increased by the heat of the sun

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热门试题

单项选择题

The rapid development of laser techniques has meant that ______.

A．surgery is likely to improve considerably
B．in another ten years we shall be able to cure cancer
C．in future all the diseases can certainly be cured
D．operations will be performed more complicatedly in the future

单项选择题

Which of the following would be appropriate to describe the instruments for surgical operations up until 1960s

A．Traditional.
B．Simple.
C．Remarkable.
D．Basic.