The statement that is proven true with an investigation of NAFTA is:
C. NAFTA resulted in job losses for some Americans but also lower prices on goods sold in the U.S.
Research and analyses conducted on NAFTA indicate that while it led to some job losses in certain sectors (particularly manufacturing), it also contributed to lower prices for consumers due to increased trade and competition. The other options contain inaccuracies or misinterpretations regarding trade agreements.