Why do Americans drive on the right-hand side of the road
while the British drive on the left?

because they're weird :) LOL

Explanation:

In the early years of English colonisation of North America, English driving customs were followed and the colonies drove on the left. After gaining independence from England, however, they were anxious to cast off all remaining links with their British colonial past and gradually changed to right-hand driving.

the correct answer is:

b) a rich merchant.