question mark

名词 question mark:

1. a punctuation mark (?) placed at the end of a sentence to indicate a question
   同义词：interrogation point

1. His identity is still a question mark to most of us.
   我们大多数人都不知道他的身份。
2. A notation, usually a question mark, calling attention to an item in order to question its validity or accuracy.
   疑问号一个记号，通常为问号，以引起对某一事物的注意以便就其有效性或准确性提出质疑