A．typedef struct student{
int num;
int age;
}STD;
STD st1;
B．struct student{
int num ,age;
}st1;
C．struct{
  int num;
float age;
}st1;
D．struct student{
  int num;
int age;
};
student st1;

A、节假日期间出现的旅客高峰
B、招生时节的考生及家长
C、“广交会”的来宾
D、老主顾