问题
单项选择题
某医师研究丹参预防冠心病的作用，实验组用丹参，对照组用无任何作用的糖丸，属于
A．实验对照
B．空白对照
C．安慰剂对照
D．标准对照
E．历史对照
答案
参考答案：C
搜题请搜索小程序“爱下问搜题”
某医师研究丹参预防冠心病的作用，实验组用丹参，对照组用无任何作用的糖丸，属于
A．实验对照
B．空白对照
C．安慰剂对照
D．标准对照
E．历史对照
参考答案：C
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Many years ago, only boys could go to school in my hometown. Then schools d ecided to let girls (1)______. But Mr Brown, one of the teachers, was not (2)_____ all pleased. He didn't want to have (3)______ girls in his class. When he began his class, Mr Brown always said: "Good morning, boys" at first. Now when girl students were in his class, he (4)______ said, "Good morning, boys." One day (5)______ only one boy in his class, others were girls. Mr Brown didn't know (6)_______. He just said, "Good morning, boy." (7)_______ day he came into his classroom and looked at all the students. There were no (8)______ in his class. He was very (9)______ and said, "Oh, nobody (10)_______today!" Then he went out of the classroom.
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