Answer:
wheeled vehicles & domesticated animals.
Step-by-step explanation:
One persistent issue because of which the native Americans were unable to overcome was the shortage of domesticated animals to assist with hard labor. Therefore they have to lift, lift and drag with their own and resulting in agricultural production becomes harder, takes more time, and is less effective. Wheeled vehicles combined with labor-intensive domesticated animals were not only a problem for agricultural production but also to the communication.