定义结构体类型变量teach1,不正确的是（）。

定义结构体类型变量teach1,不正确的是（）。
A.struct teacher {int num; int age; }; struct teacher teach1;
B.struct teacher {int num; int age; }teach1;
C.struct {int num; int age; }teach1;
D.struct {int num; int age; }teacher; struct teacher teach1;
正确答案：D