单项选择题

The origin of language is ______.

A．clearly explained in this passage
B．a matter that can not be or has not been explained or understood
C．a question that was difficult to answer
D．a problem already solved

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热门试题

单项选择题

It is necessary to pick up the words when we tell or write in order ______.

A．to show that we are polite
B．to show that we are good at using them
C．to express exactly what we mean
D．to prove that we are not silly

单项选择题

One of the reasons why men invented certain sounds to express thoughts and actions was that they could ______.

A．agree with certain signs
B．write them down
C．make themselves understand each other
D．combine them