Application questions..

So, recently I've found myself unemployed. I've been applying to various companies with no success.. but that's more of a sidenote for this...

My question is that on these online applications one of the questions is Most common truck driven with a drop down menu for you to pick one... my confusion is, which one SHOULD I pick?.. the list has "Conventional Tractor" AND "Tractor-Trailer" ... as if there is a difference between them.



Any ideas? or does it really matter if you pick conventional tractor vs. tractor-trailer?

 

thanks I just find it odd/weird that they would put tractor-trailer as an option as if it was it own special kind of vehicle that's different then a conventional tractor, day cab tractor, or cabover tractor.... x.x seriously what kind of tractor are they thinking of when they say "tractor-trailer" compared to the other types.