what letter is not "I",and it is not "he"or"she"?谜语

What letter is drink? What letter is question What letter is drink? What letter is question? What letter is you? what letter is a What letter is nothing what letter is what do you call a bear with no ear.还有两句：what letter is an insrct?what letter is in the middle of an eye? What do you call a bear with no ear.还有两句：What letter is a part of the head .What letter is a drink. What letter is a question?What letter is an insect? What letter is a drink? What letter is an insect? What letter is a drink? What letter is a drink What letter is a question? What letter is a question? what letter is an insect?