What vegetable ____________ the letter " a " ?[ ]
A. has
B. have
C. are
答案：A
数列{an}前n项和Sn=4n2-n+2，则该数列的通项公式an=______．
老年男性，腹股沟内侧半球形肿块，平卧消失，压内环站立仍出现可诊断为（）
A.腹股沟斜疝
B.腹股沟直疝
C.睾丸鞘膜积液
D.股疝
E.隐睾
