Which of the following updatable view restrictions is NOT valid?

a$.$ Set operators such as UNION, INTERSECT, and MINUS cannot be used.

b$.$ The base table to be updated must be key$-$preserved; all values of the primary key must be kept unique.

c$.$ GROUP BY expressions or aggregate functions cannot be used.

d$.$ Updatable view must include the name$($s$)$ of the base table$($s$)$ used in the view.