Consider the following statements:

struct studentType$1$

$\{$

string name;

int ID;

float gpa;

$\}$;

struct studentType$2$

$\{$

string name;

int ID;

float gpa;

$\}$;

studentType$1$ student $1,$ student $2$ ;

studentType$2$ student$3,$ student $4$ ;

Which of the following statements is valid in $C_{+}+?$

a$.$ student$2=$ student$3$;

b student! efudent $4$

$90$ tudent$210=10$

Sludent$110$ botudenta $10$