The idiom diamond cut diamond is grammatically incorrect, for normally the verb cut should take the third person singulars. 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
