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【单选题】
已知电源变压器次级电压有效值为10V,其内阻和二极管的正向电阻可忽略不计, 整流电路后无滤波电路: 若采用全波整流电路,则输出电压平均值为( )A.
12V
B.
9V
C.
4.5V
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举一反三
【单选题】Since that unfortunate accident last week, I _______________ at all well.
A.
haven’t been sleeping
B.
have been sleeping
C.
haven’t sleeping
D.
have sleeping
【单选题】下列哪种作用不属于 β 受体兴奋时的效应 prefix="o" ns="urn:schemas-microsoft-com:office:office" ?xml:namespace>
A.
支气管舒张
B.
血管扩张
C.
心脏兴奋
D.
瞳孔扩大
E.
肾素分泌
【单选题】I at all well since she left home.
A.
Wasn’t sleeping
B.
am not sleeping
C.
hadn’t slept
D.
haven’t been sleeping
【单选题】听力原文： I met Susan at a dance about six months ago. We get along well together since we like music, dancing, swimming, and tennis. But whenever I start to get serious about our relationship and try to ...
A.
The relationship between the speaker and Susan.
B.
The speaker' s arrangement of the speaker' s marriage ceremony.
C.
The parents' opinion of Susan.
D.
The speaker' s plan for the future.
【单选题】下列哪种作用不属于β受体兴奋时的效应
A.
支气管舒张
B.
血管扩张
C.
心脏兴奋 prefix='o' ns='urn:schemas-microsoft-com:office:office' ?xml:namespace>
D.
瞳孔扩大
E.
肾素分泌 prefix='o' ns='urn:schemas-microsoft-com:office:office' ?xml:namespace>
【单选题】听力原文： I met Susan at a dance about six months ago. We get along well together since we like music, dancing, swimming, and tennis. But whenever I start to get serious about our relationship and try to ...
A.
The relationship between the speaker and Susan.
B.
The arrangement of the speaker's marriage ceremony.
C.
The speaker's parents' opinion of Susan.
D.
The speaker's plan for the future.
【单选题】听力原文： I met Susan at a dance about six months ago. We get along well together since we like music, dancing, swimming, and tennis. But whenever I start to get serious about our relationship and try to ...
A.
The relationship between the speaker and Susan.
B.
The arrangement of the speaker's marriage ceremony.
C.
The speaker's parents' opinion of Susan.
D.
The speaker's plan for the future.
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