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【单选题】
在Access中，下面关于空值Null叙述错误的是（ ）。A.
尚未存储数据的字段的值
B.
空值是默认值
C.
查找空值的方法与查找空字符串相似
D.
空值的长度为零
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【单选题】The researchers have tested their spray in the lungs.
A.
Right
B.
Wrong
C.
Not mentioned
【简答题】The researchers have conducted an experiment to prove that people will act in emergencies when ______ A) they are in pairs B) they are in groups C) they are alone D) they are with their friends
【单选题】After years of ______ bee dancing, the scientist found that the dances have certain patterns.
A.
gazing
B.
watching
C.
observing
D.
viewing
【简答题】The researchers have just completed a study of driving situations.
【单选题】The researchers have conducted an experiment to prove that people will act in emergencies when______.
A.
they are in pairs
B.
they are in groups
C.
they are alone
D.
they are with their friends
【单选题】According to the researchers, the traditional treatment for bee stings is ______.
A.
widespread
B.
extremely harmful
C.
almost futile
D.
sensitizing
【单选题】The sentence in the ninth paragraph, 'researchers are not likely to have anything resembling a blood test for a mental illness soon'means that_____.
A.
mental illness can not be diagnosed by blood test.
B.
there is not a definite criterion for mental illness.
C.
researchers do not like to use blood test.
D.
techniques have gained enough progress but are still not enough for mental illness.
【单选题】以下描述是正确的是
A.
浮地电源直接由实地电源提供
B.
浮地电路和实地电路物理上完全隔离
C.
浮地电源和实地电源的参考点是等电位的
D.
实地电源由交流电源提供，浮地电源由直流电源提供
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