以下结构体类型说明和变量定义中正确的是( ) A: tupedef strct{int n;char c;};REC t1,t2; B: tupedef strct{int n;char c;}REC;REC t1,t2; C: strct{int n;char c;}REC;REC t1,t2; D: tupedef strct REC;{int n=0;char c='A';}t1,t2;