TASK DEFINITION: You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.
PROBLEM: Category: IN THE TEENS 
Clue: One of these "wheelers" is a large tractor-trailer truck rig

SOLUTION: 18-wheeler

PROBLEM: Category: HOW DO THEY WORK? 
Clue: Many car salesman work on "straight" this, though you're better off buying from one who's on salary

SOLUTION: commission

PROBLEM: Category: NURSERY RHYMES 
Clue: It's what Mary's little lamb did even though it was against the rules

SOLUTION:
followed her to school one day