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【单选题】
When the researchers excluded seven people who were already infected when the trial started, ______.A.
those seven people were in favor of the vaccine very much.
B.
the effect of vaccine was significant.
C.
it showed that people were less likely to be infected by taking vaccine.
D.
it showed the vaccine can reduce the risk of being infected for all the people.
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【单选题】— ________ Miss Brown ________ many English books? — Yes, she ________. [ ]
A.
Does, have, don't
B.
Do, have, does
C.
Does, has, does
D.
Does, have, does
【单选题】如图所示为一继电器延时电路模型。继电器参数：R=100W，L=4H，当线圈电流达到6mA时，继电器动作，将触头接通。从开关闭合到触头接通时间称为延时时间。为改变延时时间，在电路中串联一个电位器，阻值从零到900W间变化。若【图片】，试求电位器电阻值变化所引起的延时时间的变化范围。【图片】
A.
2.05ms----2.77ms
B.
20.5ms----27.7ms
C.
205ms----277ms
D.
2050ms----2770ms
【简答题】大肠杆菌pUC118质粒的某限制酶唯一酶切序列，位于该质粒的lacZ基因中，lacZ基因中如果没有插入外源基因，lacZ基因便可表达出b-半乳糖苷酶，当培养基中含有IPTG和X-gal时，X-gal便会被b-半乳糖苷酶水解成蓝色，大肠杆菌将形成蓝色菌落；如果lacZ基因中插入了外源基因，带有pUC118质粒的大肠杆菌便不能表达b-半乳糖苷酶，培养基中的X-gal不会被水解成蓝色，大肠杆菌将形成白色...
【单选题】--Does she have a tennis racket? --__________ [ ]
A.
Yes, she has.
B.
No, she hasn’t.
C.
Yes, she does
D.
No, she does.
【单选题】—Does she _____ a knife? —No, she _____. [ ]
A.
has; don't
B.
have; does
C.
have; doesn't
D.
have; has
【简答题】是唯一能溶于水的细胞色素。
【单选题】如图为一继电器延时电路模型。继电器参数：R=100W，L=4H，当线圈电流达到6mA时，继电器动作，将触头接通。从开关闭合到触头接通时间称为延时时间。为改变延时时间，在电路中串联一个电位器，阻值从零到900W间变化。若【图片】，试求电位器电阻值变化所引起的延时时间的变化范围。【图片】
A.
2.05ms----2.77ms
B.
20.5ms----27.7ms
C.
205ms----277ms
D.
2050ms----2770ms
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