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_爱下问搜题

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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，这属于

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

单项选择题

现阶段我国一般企业的安全投资应该达到项目造价的( )。

A．0.8%～2.5%
B．1.0%～3.5%
C．2.5%～4.5%
D．5.0%～7.5%

阅读理解

阅读理解。

Monday, April 17
Dear Gramps,
     I was so upset last week when somebody stole my Super Racer from the park by your house. I
called up the toy company but they said they have only red, blue and green racers. Dad called Cobb's
Toy Store today and found out they might have purple ones. Can we go there when I come to visit
you next week?
     You and I were only gone for a few minutes to the shop down the street to get ice-cream and
cookies. Maybe the thief was watching us. Mum was surprised when I told her the racer was stolen.
She said she used to leave things at the park all the time when she was young. Once she even left her
bicycle for two days near the swimming pool.
     Tell Grandma that I like the food she made last time. Ask Grandma if we can have pancakes with
sugar for breakfast when I come this time. I have packed in my towel, comb and soap. Tell her this
time I won't forget to pack in my toothbrush.
Love
Toby

1. The writer wants to have a _____ racer.

A. red
B. blue
C. green
D. purple

2. How long did the writer leave his Super Racer at the park?

A. Two days.
B. A few minutes.
C. Over a week.
D. All the time.

3. Which of the following is true?

A. Cobb's Toy Store is far from Gramps' house.
B. There were lots of thieves when Toby's mum was young.
C. The writer visited Gramps pretty often.
D. The writer took his toothbrush with him on his last visit.