The correct answer is B; The manufacturer would have access to additional markets in other countries.
The North American Trade Agreement is an agreement which was signed by The United States, Canada and Mexico in 1994. After this agreement entered into force, all the tariffs, duties and quantitative restrictions were gradually eliminated.
Thus, negotiations among those countries started. This agreement is beneficial to American manufacturers due to the fact that they can have access to much larger opportunities to find demand for their product. As a result a company can produce larger supply and expand, generating more profit for the company