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【单选题】
According to the author, why do people compare their own life with someone else’s life?A.
Because people are never satisfied with what they have got.
B.
Because people know their own problems, but don’t always see other people’s problems.
C.
Because some people have a more miserable life than others.
D.
Because there are more losers than winners in this world.
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举一反三
【单选题】数字证书提供了一种在因特网上验证你身份的方法，它的作用类似与生活中的身份证；数字证书是由权威机构（）颁发的。
A.
IETF
B.
IEEE
C.
CA
D.
CCITT