下面是Danny写的句子，帮他判断一下是(√)否(×)正确。

( ) 1. My mother's sister is my aunt.

( ) 2. My father's mother is my grandfather.

( ) 3. My father's wife is my mother.

( ) 4. My mother's brother is my uncle.

( ) 5. My aunt's father is my cousin.

在气管切开中，有助于术中数清气管环的数序的重要解剖标志是（）。

A.环状软骨

B.甲状腺峡部

C.甲状软骨

D.胸骨上窝

E.舌骨