皮皮学，免费搜题
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【单选题】
某学者通过美国研制的乙肝疫苗的随机对照试验，以确定其对乙肝母婴传播的预防效果，将对象随机分为实验组（40名）和对照组（44名），实施接种后，实验组发生HBsAg阳性1例，而对照组发生HBsAg阳性13例。这种流行病学研究方法属于（）。A.
生态学研究
B.
预防性试验
C.
队列研究
D.
临床试验
E.
病例对照研究
拍照语音搜题，微信中搜索"皮皮学"使用
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皮皮学刷刷变学霸
举一反三
【单选题】She completely lost her voice and had to give _____ teaching.
A.
with
B.
up
C.
to
D.
out
【简答题】单词拼写。 1. It was dark and he has completely lost his s______ of direction. 2. She gets c______ when her husband goes out drinking. 3. 'Every dog has his day.' is a s______, meaning that everyone gets h...
【简答题】Read the following passage that is about a girl called Sang Lan, and then write a letter to her. Sang Lan was a good gymnast (体操运动员)in China. She dreamed of going to the Olympics and being a world cha...
【单选题】She completely lost her voice and had to give ______teaching.
A.
at
B.
in
C.
down
D.
up
【简答题】She completely lost her voice and had to give _____ teaching.
【单选题】She completely lost her voice and had to give _____ teaching.
A.
to
B.
up
C.
on
D.
down
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