以下结构体类型说明和变量定义中正确的是

A) typedef struct
int n; char c; REC;
REC t1, t2;
B) struct REC;
int n; char c; ;
REC t1, t2;
C) typedef struct REC;
int n=0; char c='A'; t1, t2;
D) struct
int n; char c; REC;
REC t1, t2;