Which of the following is a valid SQL statement? a. SELECT customer#, order#, MAX(shipdate-orderdate) FROM orders GROUP BY customer# WHERE customer# = 1001; b. SELECT customer#, COUNT(order#) FROM...

Which of the following is a valid SQL statement?

a. SELECT customer#, order#, MAX(shipdate-orderdate)

FROM orders

GROUP BY customer#

WHERE customer# = 1001;

b. SELECT customer#, COUNT(order#)

FROM orders

GROUP BY customer#;

c. SELECT customer#, COUNT(order#)

FROM orders

GROUP BY COUNT(order#);

d. SELECT customer#, COUNT(order#)

FROM orders

GROUP BY order#;