Review the passage:
While cleaning under his bed, Glen heard the vacuum cleaner suck up something
hard and metallic. Glen wanted to know what the object
was. But had no intention of digging through a bag of dust, dead
bugs, cat litter, and bathroom hair to find out.
You chose the second part, Glen wanted to know what the object was. This part has a main clause: Glen is the subject; wanted is the verb. A fragment will not have a main clause.