Final answer:
The correct answer to the student's question about the opportunity cost of producing food is B. The US gives up 1 unit of clothing to produce 2 units of food.
Step-by-step explanation:
In the context of opportunity costs in production, when the US produces 1 unit of food, it gives up the opportunity to produce clothing. Since producing 1 unit of clothing costs 2 hours, the US could have produced 0.5 units of clothing in the time taken to produce 1 unit of food (1 hour). Similarly, for the EU, producing 1 unit of food takes 3 hours; it could have produced 0.75 units of clothing in that time (since 1 unit of clothing takes 4 hours there). Therefore, the opportunity costs of producing food are different for the US and EU.
This means that the correct answer is B. The US gives up 1 unit of clothing to produce 2 units of food. A is incorrect because the US gives up 0.5 units of clothing per unit of food, not 2. C and D pertain to the EU and are therefore not applicable to the US's opportunity cost for producing food. However, regarding the EU, neither C nor D is correct, since they don't reflect the proper conversion of the EU's labor hours into units of clothing.