血IgA降低，IgG、IgM升高见于
A．甲状腺功能减低症B．苯丙酮尿症C．胸腺发育不全D．21-三体综合征E．手足搐搦症
参考答案：E
You have to be accurate in this job, because a small mistake can make a big ________. [ ]
A. difference
B. difficulty
C. trouble
D. change
重症肌无力：
