设总体X～P(λ)，X 1 , …,X n 是来自X的一个样本，X bar 为样本均值，则E(X bar )=_______，D(X bar )=_______。

Which of the following are NOT valid if/else statements in Python, assuming x and y are defined appropriately: A: if x < y: print('foo') else: print('bar') B: if x < y and x > 10: print('foo') C: if x < y: print('foo'); print('bar'); print('baz') D: if x < y: print('foo') elif y < x: print('bar') else: print('baz')

在Java script中,运行下面代码的结果是 function foo(x){ var num=5; bar=function(y){ return (x+y+(++num)); } } console.log(foo(2)); console.log(bar(10)); console.log(bar(10));"

（2）、$A,B,C$至少两个发生 A: ${(ABC)}\cup{(\bar{A}BC)}\cup{(A\bar{B}C)}\cup{(AB\bar{C})}$ B: ${(\bar{A}BC)}\cup{(A\bar{B}C)}\cup{(AB\bar{C})}$ C: ${A}\cup{B}\cup{C}$ D: ${(\bar{A}\bar{B}\bar{C})}\cup{(\bar{A}B\bar{C})}\cup{(\bar{A}\bar{B}C)}\cup{(A\bar{B}\bar{C})}$

绘制变量x和y的散点图的R命令是( ) A: plot(x,y) B: bar(x) C: hist(x) D: pie(x)

There are different kinds of bar, you can see main bar, __________,(酒廊) grand bar, __________, (茶室)service bar, banquet bar, __________(主题酒吧), and gentle bar.

题目包含多个选项，但学生只能选择一个答案。<br/>设A,B,C表示三个随机事件，请问下列事件应如何用A,B,C表示<br/>（2）、$A,B,C$至少两个发生 A: ${(ABC)}\cup{(\bar{A}BC)}\cup{(A\bar{B}C)}\cup{(AB\bar{C})}$ B: ${(\bar{A}BC)}\cup{(A\bar{B}C)}\cup{(AB\bar{C})}$ C: ${A}\cup{B}\cup{C}$ D: ${(\bar{A}\bar{B}\bar{C})}\cup{(\bar{A}B\bar{C})}\cup{(\bar{A}\bar{B}C)}\cup{(A\bar{B}\bar{C})}$

JFrame对象（窗框）添加菜单条对象bar，用那个方法？ A: add(bar) B: setJMenuBar(bar); C: setBar(bar); D: addJMenuBar(bar);

_______ rules may change the syntactic representation of a sentence.? Transformational|X-bar|;Generative|;Phrase structure

设RS触发器有两个输入端$$$\&#91;\bar R\&#93;###和$$$\&#91;\bar S\&#93;###，有两个输出端Q和$$$\&#91;\bar Q\&#93;###。如果要是触发器为“0”状态，则两个输入端应为 A: $$$\[\bar S\]###=0，$$$\[\bar R\]###=0 B: $$$\[\bar S\]###=0,$$$\[\bar R\]###=1 C: $$$\[\bar S\]###=1,$$$\[\bar R\]###=0 D: $$$\[\bar S\]###=1,$$$\[\bar R\]###=1