trade agreements are helpful because they allow countries to\n○ trade for necessary goods.\n○ increase trade…

Brief Explanations:

Trade agreements aim to facilitate international trade. One of their main purposes is to enable countries to access goods they need. Trade agreements typically reduce trade barriers (so "help create new trade barriers" is wrong). They don't focus on increasing trade - tax revenue (as that would be more of a protectionist measure, contrary to the spirit of trade agreements). And while they can have an impact on foreign trade, the core and most fundamental positive aspect is allowing trade for necessary goods.

Answer:

trade for necessary goods.