The idiom diamond cut diamond is grammatically incorrect， for normally the verb cut should take the third person singular -s. However， we use it as it is. This shows that（）.

The idiom diamond cut diamond is grammatically incorrect， for normally the verb cut should take the third person singular -s. However， we use it as it is. This shows that（）.
A、many idioms are grammatically unanalysable
B、the word order of idioms cannot be inverted or changed
C、the structure of an idiom is to a large extent unchangeable
D、the constituents of an idiom cannot be deleted or added to
正确答案：A