During a science class on weather, the instructor wanted to discuss the concept of sublimation, the act of going from a gas to a solid skipping the intermediate liquid stage. He gave as an example water vapor in the air condensing on a car's windshield to form ice. 

Wanting to see if the class had understood the concept, the instructor asked if anyone could provide an example of something that went straight from a solid to a gas. He was expecting "dry ice" as the answer. 

One of the students blurted out, "Burritos."