Answer:
a. the horse.
Step-by-step explanation:
Because they could go farther and more quickly with the aid of horses, pastoral groups were able to significantly expand their area as a result of the domestication and usage of horses. They were also able to employ horses for hunting and shift their herds to different grazing areas. Horses were useful in both fighting and the movement of commodities.
The invention of the compass, paper money, and iron smelting were all significant technological advances, but they had little direct bearing on the spread of pastoral settlements.