The factor that helped the United States in making the inland transportation and commerce to be possible is in letter C. The intricate river system. I hope you are satisfied with my answer and feel free to ask for more if you have clarifications and questions.
The faster magma cools the thinner its crystals become
PRECIPITATION,TEMPERATURE, VEGETATION
1, I want to say in the mid atlantic.
2. you use the scale on the bottom left to answer so it 1cm=405km.
3. I think you pick a line on the picture and that's the age, but I'm not to sure because I don't see a key. I hope this helps.