Task: Question Answering
Input (English): Passage: Administrators at Mildew College, an all-girl school, are begging the school's largest benefactor, Mrs. Catsby, to provide an athletic fund for the school. She does not approve of girls playing sports, and informs the administrators that the money will be used for the salaries of the three new Teutonic professors that are arriving that day. Meanwhile, the Stooges have just started a new job as servicemen at a service station, with a strong held belief of "super soyvice!" When they get a customer (three older German men driven by a chauffeur), they proceed to provide their own inept brand of service, angering the men. The mayhem ends when Curly accidentally puts gasoline in the radiator and Moe checks it with a match. The resulting explosion wrecks the car and prompts the Stooges to flee in a nearby ice cream truck that they had coincidentally thrown the German men's suitcases into. Curly climbs in the back while Moe and Larry are in the front.
The Stooges finally stop when they run out of gas. Moe and Larry realize that Curly is still in the back of the truck and is now frozen solid. They thaw him out by tying him to a tree branch over an open fire. This works fine until Curly wakes up on fire and jumps into a nearby lake. When Moe and Larry try to help him out, he pulls them in with him. Now soaked, the boys decide to see if there are any dry clothes in the suitcases they had thrown into the truck.
The suitcases, it turns out, belong to the three new professors for Mildew College, and as the boys, now decked in their gowns and mortarboards, try to hitch a ride, Mrs. Catsby spots them and picks them up, bringing them to the school. During the introductions of the "new professors," a student gets wise with a nonplussed Larry, and in order to test their "mental coordination", Moe begins a rendition of "Swingin' the Alphabet", which starts off fine and eventually transcends into a jazzy, off-time performance. 
Question: What causes Curly to freeze?
Output (English): ice cream truck.