A bobtail is:

A tractor without a trailer.. Definition: Bobtail = Tractor only.

A bobtail is:

ANSWER BREAKDOWN
  • A. Correct. Definition: Bobtail = Tractor only.
  • B. Incorrect. "A trailer without a tractor." is not correct. Definition: Bobtail = Tractor only.
  • C. Incorrect. "A short trailer." is not correct. Definition: Bobtail = Tractor only.
  • D. Incorrect. "A cat." is not correct. Definition: Bobtail = Tractor only.