Why is it important for canada and the united states to work together to reduce pollution?

The United States and Canada are two countries that are highly developed, and produce a lot of pollution, be it in the air, water, or the soil. These two countries have a free economy going on between them, so the collaboration is very intense and mutually dependent, and on top of that, these two countries share some of the same ecological systems.

The pollution is doing no good to anyone, not to the environment, which is being destroyed, nor to the humans, which are having health issues because of it. So these two countries should use the fact that they are in lot of ways united, and with combined forces and efforts to stop the pollution, or at least minimize it, for the well-being of their future, the future of their inhabitants, the environment, and the world as a whole.

it sounds like either a or c