3.正確的C語言標識符是（）9.一個C程序是由（）2x1A．;floatx,y,z;scanf("x=%d,y=%d,z=%d",&a,&y,&z)D．└┘y=2└┘B．scanf("%f%f",&x,&y)A．scanf("%c%c%c",&s1,&s2,&s3){intx=2,y=3;A.x=%2,y=%3C.x=2,y=3{inta;A．scanf("%d%f",&a,&b);D．scanf("%d%d%c%c%c%c%c%c",&x,&y,&s1,&s1,&s2,&s2,{intx1,x2;x+=y;y=x-y;x-=y;intu;floatv;scanf("%3d%f",&u,&v);2．B3．A4．B5．B6．D8．D9．B10．Cextern,for,float,goto,if,int,int,long,register,return,elseif(x==0)y=0;elseif(x<0)y=-1;{casec1:y=a-b;case0:y=a-b;casec2:{default:y=a*b;default：printf("gradeiserror!\n");default：printf("gradeiserror!\n");default：printf("gradeiserror!\n");default：printf("gradeiserror!\n");{case0:m++;break;{default:m++;if(a>50)printf("%d",a);if(a>40)printf("%d",a);if(a>30)printf("%d",a);printf("%d%d%d",s,w,t);elseprintf("thesinglerootis%f\n",-c/b);printf("complexroot\nrealpart=%fimagpart=%f\n",printf("pleaseinputtheyeartojudewhetheritisaleapif(【1】)ch=ch+32;elseif(ch>='a'&&ch<='z')printf("theaccountpayableofthewatermelonis%f\n",charch1='a',ch2='A';elserate=【2】;{case-y=0;{case'+':printf("%g%c%g=%g\n",x,operator,y,x+y);case'-':printf("%g%c%g=%g\n",x,operator,y,x-y);case'/':if(y==0.0)printf("%g%c%g=%g\n",x,operator,y,C.循環(huán)體將執(zhí)行無數(shù)多次do{w--；printf(〞*〞)；}{w=u%v；u=v；for(;i<=100;i++)sum+=i;k1=1;k2=2;k3=3;x=15;if(!k1)x--;elseif(k2)if(i<=0)printf("****\n");elseprintf("%%%%\n");