The origin of language is _____________.
A.a legend handed down from the past
B.a matter that is hidden or secret
C.a question difficult to answer
D.a problem not yet solved
正确答案是D
The origin of language is _____________.
A.a legend handed down from the past
B.a matter that is hidden or secret
C.a question difficult to answer
D.a problem not yet solved
正确答案是D