假设变量sum=0和j=80都是int类型，则下列语句中的正确的是( ).

A．if (true) System. out. println("true"); else;

B．if (5＜＞1) System. out. println( "not equal" );

C．for (iht j=20;j＜＜50;j--) System. out. println (j);

D．while (j＞＞=50) sum +=j; j--;