The facility that allows nesting one select statement into another is . . . . . . . .

Imagine you have a big box of toys. You want to find all the blue toys, but there are too many to look through. You could make a smaller box and put only the blue toys in it. This smaller box is like a subquery in SQL.

A subquery is a select statement inside another select statement. It's like a smaller search within a bigger search.

So the answer is Option C: subquerying.