If the trailer is too low for coupling, you should:
Correct. Use the landing gear hand crank to raise the trailer to the proper height (just below fifth-wheel level) before backing under.
CDL Practice Question #206
Category: Combination Vehicles
Why this question matters
This question is one of 55 in our Combination Vehicles bank. The reasoning above comes directly from the AAMVA CDL Manual, the source document used by every U.S. state DMV. Memorizing the underlying rule — not just the letter answer — is what separates passing on the first attempt from a return trip and another fee.