Which of the following statements would create a UNION between all of the cities we have customers, employees, or invoices in$?$

SELECT billing$\_$city

FROM invoice

UNION

SELECT city

FROM customer

UNION

SELECT city

FROM employee;

SELECT billing$\_$city

FROM invoice

SELECT city

FROM customer

SELECT city

FROM employee;

SELECT city

FROM invoice

UNION

SELECT city

FROM customer

UNION

SELECT city

FROM employee;

SELECT billing$\_$city

FROM invoice

SELECT city

FROM customer

SELECT city

FROM employee

UNION;