Explanation:

• Option 1 says the common price level is important because domestic prices vary a lot between countries. That’s totally true—it’s hard to compare economic output if a loaf of bread costs $1 in one country and $5 in another.

• Option 2 points out that “100 GDP” in one country isn’t the same as “100 GDP” in another. Absolutely right. The same number doesn’t buy you the same amount of goods, so using a common measure (like purchasing power parity, or PPP) gives us a fairer comparison.

• Option 3 gives us both reasons—makes sense, since both statements get to why standardizing price levels matters.

• Option 4 is just “none,” and obviously, that’s not the case here.

Option 3 is the correct answer.