以下C语言程序错误行的地方有哪些? #include " stdio.h " main( ) { int a,b ; sum ; a=123; b=456; sum= a+b ; printf ( " sum is %d \ n " ,sum , ); return 0; } (10.0分) A. #include " stdio.h " B. main( ) C. int a,b;sum ; D. a=123; b=456; E. printf ( " sum is %d\n " ,sum, );