某RLC串联电路的有功功率为30W，无功功率为40Var，则电源的视在功率为

Cans of soft drinks cost $0.30 in a certain vending machine. What is the expected value and variance of daily revenue (Y) from the machine, if X, the number of cans sold per day has E(X) = 90, and Var(X) = 40 ( ) A: E(Y ) = 27, Var(Y ) = 4.5 B: E(Y ) = 27 , Var(Y ) = 4.5 C: E(Y ) = 27 , Var(Y ) = 3.6 D: E(Y ) = 90 , Var(Y ) = 3.6

1802d0f3aa3f66d.jpg图示正弦稳态电路电压源发出的无功功率为 A: 20var B: -20var C: 40var D: 0var

设随机变量X的方差存在，Var(X)>0，则以下结论正确的是 A: Var(X) > Var(1－X) B: Var(X) < Var(1－X) C: Var(X) = Var(1－X) D: Var(X) + Var(1－X) = 1

main() { int var, *p; var=100; *p=&amp;var; var=*p+10; printf("%d",var); }运行结果：

根据下面的定义，F0(3+4)的输出结果是_______（注意没有空格）#defineF1(var)printf("var=%d",var)#defineF0(var)F1(var*var)

设Varξ=Varη=Var(ξ-2η)=1, 则COV(ξ,η)=______

以下打印的结果是？ <?php $var='a';$VAR='b';echo"$var$VAR"; A: aa B: C: a

与以下JavaScript代码var hello等价的代码是（ ）。 A: var HEllo B: var Hello C: var hello D: var HELLO

Date对象问题4：Date对象正确获取年份的方法是： A: var now = new Date();var year = now.Year(); B: var now = new Date();var year = now.getYear(); C: var now = new Date();var year = now.getFullYear(); D: var now = new Date();var year = now.getNowYear();