19 - May you please help me?

Which of the following can never be true?

1Americans in 2019 had a comparative advantage over the Canadians in producing lumber but in 2020 have a comparative disadvantage to the Canadians in producing lumber.

2Americans' average wages rise when Americans start trading more with low-wage countries.

3Americans have a comparative disadvantage in the production of every good or service that it is possible to produce.

4China's current-account surplusandChina's capital-account deficit both fall simultaneouslyand by the exact same amount.