选择题：2*51.以下叙述正确的是：A.接口中一定要有虚方法。B.一个类可以实现多个接口。C.接口能被实例化。D.接口中可以包含已实现的方法。2.int[][]myArray3=newint[3][]{newint[3]{5,6,2},newint[5]{6,9,7,8,3},newint[2]{3,2}};myArray3[2][2]的值是（）。A.9B.2C.6D.越界3.此程序输出结果是:abstractclassBaseClass{publicvirtualvoidMethodA(){Console.WriteLine("BaseClass");}publicvirtualvoidMethodB(){}}classClass1:BaseClass{publicvoidMethodA(){Console.WriteLine("Class1");}publicoverridevoidMethodB(){}}classMainClass{publicstaticvoidMain(string[]args){BaseClasso=newClass1();o.MethodA();}}A.BaseClassB.BassClassClass1C.Class1D.Class1BassClass4.如下程序的运行结果是：publicabstractclassA{publicA(){Console.WriteLine('A');}publicvirtualvoidFun(){Console.WriteLine("A.Fun()");}}publicclassB:A{publicB(){Console.WriteLine('B');}publicnewvoidFun(){Console.WriteLine("B.Fun()");}publicstaticvoidMain(){Aa=newB();a.Fun();}}A.ABA.Fun()B.ABB.Fun()C.BAA.Fun()D.BAB.Fun()5.C#中以下那个是正确的字符串声明?*1.strings=#”nTeststring”;2.strings=“’nTeststring”;3.strings=@”nTeststring”;4.strings=“nTeststring”;判断题：2*５1.C#中不支持抽象类。2.C#中没有头文件并且在同一处声明和定义类的成员。3.C#中要在派生类中重新定义基类的虚函数必须在前面加Override。4.c#中的三元运算符是？：。5.floatf=-123.567F;inti=(int)f;此时程序出现错误?看程序，写结果：4*51.C#中，执行以下代码后S的结果：string[]a=newstring[5];aa[0]="33";aa[6]="66";strings="";foreach(stringminaa)s+=m;2.写出程序的输出结果：publicclassA{publicvirtualvoidFun1(inti){Console.WriteLine(i);}publicvoidFun2(Aa){a.Fun1(1);Fun1(5);}}publicclassB:A{publicoverridevoidFun1(inti){base.Fun1(i+1);}publicstaticvoidMain(){Bb=newB();Aa=newA();a.Fun2(b);b.Fun2(a);}}3.写出程序的输出结果publicabstractclassA{publicA(){Console.WriteLine('A');}publicvirtualvoidFun(){Console.WriteLine("A.Fun()");}}publicclassB:A{publicB(){Console.WriteLine('B');}publicnewvoidFun(){Console.WriteLine("B.Fun()");}publicstaticvoidMain(){Aa=newB();a.Fun();}}4.写出程序的输出结果classClass1{privatestringstr="Class1.str";privateinti=0;staticvoidStringConvert(strings){s="