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;