人体缺少哪种元素会引起甲状腺肿大，俗称大脖子病？
参考答案：
人体缺少碘会引起甲状腺肿大。
When _____ you have a school trip? Sorry, I _____ know. [ ]
A. are, don't
B. do, aren't
C. are, aren't
D. do, don't
以下选项中，值为1的表达式是( )。
A．1-'0'
B．1-'\0'
C．'1'-0
D．'\0'-'0'
