The text calls the type of comparative advantage that is not easily changed, such as climate:

Basis may change if

A. a new ethanol plants is built locally. B. a large capacity train terminal is built by CGB. C. a drought resulted in a short crop. D. All of the above.

For the past 15 years the American public has wanted to buy big trucks. The Big Three automakers delivered, investing billions in plants that build gas guzzlers. Now, when customers walk into showrooms, gas mileage is on their mind

Retooling the industry will take years, so in the meantime GM, Ford and Chrysler are tweaking their existing models. They're changing tires, adjusting transmissions and exhaust valves in hopes of getting one or maybe two more miles per gallon. Which of the decisions by the Big Three to gain gas mileage is a short run decision? A) adjusting exhaust valves B) adjusting transmissions C) changing tires D) All of these decisions are short run decisions.