皮皮学，免费搜题
登录
搜题
【单选题】
筛选ALT正常、HBV全阴性的5～9岁小学生180名作为研究对象，用随机数字表分成两组。在研究对象和研究者都不了解分组情况条件下，一组接种国产疫苗，一组注射安慰剂，接种9年后检测，发现疫苗组HBV人年感染率为1.72%，安慰剂组为9.25%。本实验采用的方法是（）。A.
单盲
B.
双盲
C.
三盲
D.
开放实验
E.
非盲法
拍照语音搜题，微信中搜索"皮皮学"使用
参考答案：
参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【单选题】—Peter looked tired and a little absent－minded at the meeting． —He _____ up too late．A．may stayB．
A.
30．—Peter looked tired and a little absent-minded at the meeting． —He _____ up too late． A．may stay
B.
could stay
C.
should have stayed
D.
must have stayed
【单选题】Which is right(正确的)?A． Frank is Peter's brother． B．Kevin and Peter are cousins．C
A.
30． Which is right(正确的)? A． Frank is Peter's brother．
B.
Kevin and Peter are cousins．
C.
Bruce and Frank are cousins．
D.
Ruth Collins is Peter's aunt．
【单选题】听力原文：M: I really can't understand why Peter isn't here yet. We agree to meet at 8:30. It's almost 9:00. Do you think we should leave for the airport? W: He probably got into some trouble with the traf...
A.
Leave for the airport.
B.
Look for Peter.
C.
Remove the trouble for Peter.
D.
Wait a little longer.
相关题目：