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【单选题】
下列哪项属于系统误差:( )。A.
称量时天平有微小波
B.
滴定管第四位读数不准确
C.
检测未知水样pH时仪器未校正
D.
读数时把某数字8看为3
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举一反三
【单选题】For a causal relationship to exist there must be evidence
A.
of an empirical correlation between the variables.
B.
that one variable precedes the other in time.
C.
that a third variable did not cause the changes observed in the first two variables.
D.
that one variable precedes the other in time and that the two variables are correlated.
E.
that one variable precedes the other in time, that the two variables are correlated and that this relationship is not spurious.
【单选题】Which environment variable must be changed in auser’s profile so that upon login，the command prompt identifies the server？（）
A.
PMT
B.
PS1
C.
PRT
D.
PT1
【单选题】If average fixed costs equal $60 and average total costs equal $120 when output is 100, the total variable cost must be
A.
40
B.
60
C.
6000
D.
8000
【单选题】You need to retrieve the username cookie from an HTTP request. If this cookie does NOT exist, then the c variable will be null. Which code snippet must be used to retrieve this cookie object?
A.
Cookie c = request.getCookie("username");
B.
Cookie c = null; for ( Iterator i = request.getCookies(); i.hasNext(); ) { Cookie o = (Cookie) i.next(); if ( o.getName().equals("username") ) { c = o; break; } }
C.
Cookie c = null; for ( Enumeration e = request.getCookies(); e.hasMoreElements(); ) { Cookie o = (Cookie) e.nextElement(); if ( o.getName().equals("username") ) { c = o; break; } }
D.
Cookie c = null; Cookie[] cookies = request.getCookies(); for ( int i = 0; i < cookies.length; i++ ) { if ( cookies[i].getName().equals("username") ) { c=cookies[i]; break; } }
【单选题】Rose, who grows geraniums to sell, is currently producing a level of output at which her marginal cost equals her average variable cost. What must be true about Rose's average total cost at this level...
A.
It is at a minimum.
B.
It is at a maximum.
C.
It is falling with increased output.
D.
It is equal to average variable cost.
【简答题】 p____ a. 最重要的 n. 负责人,校长
【单选题】A class design requires that a particular member variable must be accesible for direct access by any subclasses of this class, otherwise not by classes which are not members of the same package. What ...
A.
The variable should be marked public
B.
The variable should be marked private
C.
The variable should be marked protected
D.
The variable should have no special access modifier
【单选题】If a function needs to modify more than one variable, it must
A.
be pass by value
B.
be a void function
C.
return all values needed
D.
be a call by reference function
【单选题】A variable must be defined ________.
A.
in every program
B.
and initialized at the same time
C.
once it has been used
D.
before it can be used
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