Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: So I did . Then , at the bottom of the Coquihalla Highway , there was an East Indian fellow who got out of his truck scratching his head at the great plumes of smoke billowing out from the wheels of his trailer . Looks like he got an expensive lesson on why you 're not supposed to ride the brakes going down a hill .. I do n't feel sorry for him , but I am very glad nobody was hurt ... The rest of the trip to Van went without incident .

Question: What is the reason great plumes of smoke billowing out from the wheels of his trailer ?
He drove the truck in a gear that was too high down the slope .
He rode the brakes going down a hill.