【单选题】
下列（）对结构类型变量定义是错误的。
①
structteacher{intnum;intage;}teach1;
②
struct{intnum;intage;}teach1,teach2;
③
struct{intnum;intage;}teacher;structteacherteach1;
④
structteacher{intnum;intage;};structteacherteach1;
【单选题】
下列（）对结构类型变量定义是错误的。
①
struct teacher {int num; int age; } teach1;
②
struct {int num; int age; } teach1, teach2;
③
struct {int num; int age; } teacher; struct teacher teach1;
④
struct teacher {int num; int age; } ; struct teacher teach1;