Which government agency is responsible for protecting the nation’s transportation systems to ensure freedom of movement for passengers and commerce?

Respuesta :

 The glorious TSA :) Transportation Security Administration. :P

Hope this helps. 
The correct answer is Transportation Security Administration

They are an agency that organizes numerous things that are related to transportation security. Among other things, they regulate things such as quality of roads or railroads, or they participate in establishing safety standards for various types of vehicles, from cars to boats and airplanes and trucks, and they do various other things.