Which of the following queries would check for duplicates of a customer$\_$id in the invoice table and how many there are of each?

a$.)$

SELECT customer$\_$id$,$ COUNT$(*)$

FROM customer

GROUP BY customer$\_$id

HAVING COUNT$(*)>1$;

b$.)$

SELECT customer$\_$id

FROM invoice

GROUP BY customer$\_$id

HAVING COUNT$(*)>1$;

c$.)$

SELECT customer$\_$id$,$ COUNT$(*)$

FROM invoice

GROUP BY customer$\_$id

HAVING COUNT$(*)>1$;

d$.)$

SELECT customer$\_$id

FROM invoice

GROUP BY invoice$\_$id

HAVING COUNT$(*)>1$;