What was unique about the building of the Panama Canal? A. It is one long canal channel through the jungle b. It used a series of locks and lakes to cross the area c. It had a set of four lakes to travel through d. It was completed in a record time of 3 years

b it used a series of locks and lakes to cross the area.

Explanation:

The Panama Canal is an artificial waterway that uses canal locks on each side to lift ships up to an artificial lake 85 feet above sea level and then lower the ships on the other side.  

So it is not just one long canal channel, it doesn´t have a set of four lakes (only one) and it took the US a little longer than three years to complete the project that France had started, namely 10 years.

because mexico wanted to choose a centralized location

a.

congress passed laws allowing for free passage between states.