单项选择题

A．Those for kids are more expensive than for adults.
B．They are all made of optical glass.
C．They are becoming more and more expensive.
D．They can be made much lighter than befor
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单项选择题
A．They cannot protect the eyes. when the sun is strong.B．They can be used as fashionable toys for kids.C．They are all fashionable.D．They do not effectively filter out harmful rays.
A．They cannot protect the eyes. when the sun is strong.
B．They can be used as fashionable toys for kids.
C．They are all fashionable.
D．They do not effectively filter out harmful rays.
单项选择题
A．are less sensitiveB．open and close more quicklyC．take in more raysD．filter out ultra-violet rays less sufficiently
A．are less sensitive
B．open and close more quickly
C．take in more rays
D．filter out ultra-violet rays less sufficiently
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