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【单选题】
引起人获得性免疫缺陷症的病毒(HIV)是:A.
DNA
B.
DNA
C.
RNA
D.
RNA
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【简答题】在如下图所示电路中，变压器内阻及二极管的正向电阻均可忽略不计，变压器二次电压的有效值U 2 =20V，正常工作时测得整流滤波后的平均电压U I =24V，U O =6V，C=100μF，R=400Ω，R L =400Ω。
【简答题】A．Geology. B．Music. C．Medical. D．Mathematics.
【单选题】如图所示电路, 变压器内阻及二极管正向电阻均可忽略不计, 设输出电压平均值 U O ( AV ) = 18V ,则变压器次级电压有效值 U 2 约为多少伏?
A.
18V
B.
20V
C.
15V
D.
24V
【简答题】It is a medical condition that produces an unfavorable reaction to certain foods,insect bites,etc.
【单选题】As the cost of gas and oil for home heating has gone up, many Americans have switched from these fuels to wood for heating their homes. In 1973, approximately 200,000 wood-burning stoves, intended for...
A.
went up fivefold over a six-year period
B.
rose to seven million during the seventies
C.
multiplied thirty-five times between 1973 and the beginning of 1981
D.
increased by 6,000,000 over an eight-year period
【简答题】( )症状是指能反映疾病临床特征的症状,但这些症状不能确定疾病的性质。
【简答题】A) chemical B) physical C) medical D) mental
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