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 main idea of this passage is ______.

A．one type of people becomes happy.
B．one type of people becomes miserable.
C．the happy people enjoy all the cheerful things.
D．there are two types of people in the world.

单项选择题

If such unhappy persons don't change their bad behavior, the author's solution to the problem is that ______.

A．people should avoid contact with them
B．people should criticize their misconduct
C．people should help them recognize the bad effects
D．people should show no respect and politeness to them