When backing a tractor under a trailer, you should expect that `________________`.

A the trailer will be lifted slightly when the tractor backs under it.

explanation

The trailer should be low enough that it is raised slightly by the tractor when the tractor is backed under it. Raise or lower the trailer as needed. (If the trailer is too low, the tractor may strike and damage the trailer nose; if the trailer is too high, it may not couple correctly.) [Commercial Driver Handbook]