I'm completely stuck on this question..

Trade barriers only work when..?
-infant industries receive the protection.
-the United States does not have a trade deficit.
-American money is kept in the United States.
-other countries do not use trade barriers.

I want to say the answer is the 2nd one...the 1st and 3rd don't seem to fit with this, and I'm not sure about the last answer which is why I don't know the answer..

can anyone please help me?

There are a few reasons why trade barriers can be a good idea (so I'm bothered by the word "only") That said, the most-cited reason for trade barriers is the protection of infant industries. I would go with 1)