皮皮学，免费搜题
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【单选题】
When you are going to put out a fire, youA.
must be careful
B.
should keep air away from it
C.
must know it is dangerous
D.
should cover it with water
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举一反三
【单选题】Please don't take ______ at what I'm saying.
A.
defence
B.
offence
C.
declaration
D.
obedience
【判断题】Don't take offence ——getting the form of adress "wrong" is rarely intended to be offensive.
A.
正确
B.
错误
【多选题】延伸温度应有如下特点 ( )
A.
一般为 72 ℃
B.
PCR 延伸时间越长 , 产物的得率越高
C.
Taq DNA 酶在延伸温度时有较高的酶活性
D.
PCR 延伸时间根据待扩增片断的长度而定
【判断题】Don't take offence—getting the form of address "wrong" is rarely intended to be offensive.
A.
正确
B.
错误
【简答题】PCR反应时,延伸温度一般为( ) °C ,退火温度一般比引物的Tm值要( )(填高或低)。
【判断题】PCR引物长度一般为15～30个核苷酸。过短影响PCR的特异性，过长会提高相应退火温度，使延伸温度超过TaqDNA聚合酶最适温度74℃,影响产物的生成。
A.
正确
B.
错误
【简答题】E-mail lives somewhere between a phone call and a formal letter : it can be unprepared or carefully constructed. The trouble is that you cannot always be sure how the recipient (收件人) is going to inter...
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