以下结构体类型说明和变量定义中正确的是

• A.struct REC ;
  
  { int n; char c; };
  
  REC t1,t2;

• B.typedef struct
  
  { int n; char c; } REC;
  
  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;