Answer:
The correct answer would be option B) When Columbus landed in America, the chief reason that he thought he had landed in "the Indies" was his firm belief that he had sailed far enough westward to reach them.
Explanation:
Columbus was trying to find a direct water route west from Europe to Asia when he stumbled upon the Americas which, in fact, were not actually the Americas since although they were already habitated, they still didn't have a name.
So, when Columbus arrived to the Americas in his pursue of conquest, it was by sailing west across the other side instead of doing it around the extensive African continent under the idea that the circumference of the Earth was smaller than it is.
I hope it helps!