Question

Wheel sensor assemblies are comprised of a toothed tone wheel and a pick-up assembly that do not touch each other. A(n) _____________________ must maintain a specific clearance between the two

Answer 1

Answer is Air Gap

This is just a small gap between the two that maintains the perfect distance or "clearance". If I'm reading the same textbook, it can be found on page 247 under "wheel speed sensors".