In R. Carver's short story "Tell the women we're going", two young husbands, Jerry and Bill, leave a boring Sunday afternoon family meeting for "a little run" ("Guy's got to get out", as Jerry puts it.)

After shooting a few balls and drinking a few beers, the guys get back to their car, and the story continues thus:

------------
Back on the highway, Jerry opened it up - little jumps of eighty-five and ninety. They'd just passed an old pickup loaded with furniture when they saw the two girls [on their bicycles].
"Look at that!" Jerry said, slowing. "I could use some of that."
Jerry drove another mile or so and then pulled off the road. "Let's go back," Jerry said, "Let's try it."
"Jesus," Bill said. "I don't know."
"I could use some," Jerry said.
Bill said, "Yeah, but I don't know."
"For Christ's sake," Jerry said.
Bill glanced at his watch and then looked all around. He said, "You do the talking. I'm rusty."
Jerry hooted as he whipped the car around.
---------------

Now here's my question for you native speakers of American English:When Jerry hoots, what does he do:

a) he sounds the horn of his car
b) he laughs loudly
c) he does something else (please specify) ?

If you think both a) and b) could be possible, what was your first thought?

Thanks for any comments

Godot