9. i can travel upriver against the current. i am fast, efficient, and fun. i can carry lots of people, goods, and raw materials up and down rivers easily at 10 miles per hour. i the cities that live along the river grow into larger cities. what am i?

10. i reduced the time it takes to travel over land. unlike many other forms of transportation, i can be used year-round and carry heavy loads. what am i?

11. the use of steam power really did revolutionize transportation. however, in the beginning, steam power in boats and trains had a few disadvantages. name two of them.