Question $2$ Write sql code

Not yet answered Marked out of $2\mathrm{.}00$

which of the following is an invalid SQL query?

a$.$ SELECT last$\_$name, department$\_$name FROM departments natural JOIN employees where department$\_$id $=80$;

b$.$ SELECT last$\_$name, department$\_$name FROM employees natural JOIN departments where employees.department$\_$id $=50$;

c$.$ SELECT last$\_$name, department$\_$name FROM employees natural JOIN departments ;

d$.$ None of the mentioned

e$.$ SELECT last$\_$name, department$\_$name FROM employees natural JOIN departments where department$\_$id $=50$;