When backing under the trailer, air lines `_________`.

A Should be supported out of the way.

explanation

STEP 7: Connect Air Lines to Trailer
Check glad hand seals and connect tractor emergency air line to trailer emergency glad hand.
Check glad hand seals and connect tractor service air line to trailer service glad hand.
Make sure air lines are safely supported where they will not be crushed or caught while tractor is backing under the trailer.