Refusing to accept the conventional wisdom that the earth was flat, Christopher Columbus pressed tirelessly for royal support for a westward voyage to Asia, enduring several rejections before securing approval and financing from Spain's King Ferdinand in 1492.

A) Refusing to accept the conventional wisdom that the earth was flat, Christopher Columbus pressed tirelessly for royal support for a westward voyage to Asia, enduring several rejections before securing

I could not say whether this option is correct or there is any minor flaw in it. So kept at bay.

B)Christopher Columbus refused to accept the conventional wisdom of the earth being flat; he pressed tirelessly for royal support for a westward voyage to Asia and endured several rejections, finally securing
This is incorrect for 2 reasons
1. usage of being. Earth was flat is a theory which is not true for certain period. so Incorrect meaning.
2. He did not endure rejections resulting in approval. He endure them until he got approval.

C) Refusing to accept the conventional wisdom of the earth being flat, Christopher Columbus pressed tirelessly for royal support to sail westward to Asia and to endure several rejections; he finally secured
This is incorrect for 2 reasons
1. usage of being repeats here from option B. Earth was flat is a theory which is not true for certain period. so Incorrect meaning.
2. Columbus did not press for royal support to endure rejections. Meaning error.


D) Christopher Columbus not only refused to accept the conventional wisdom that the earth was flat, he pressed tirelessly for royal support for a westward voyage to Asia, endured several rejections, and he finally secured
This is incorrect for 2 reasons
1. incorrect usage of idiom not only...but also.
2. pressing, enduring and securing are not consecutive events.

E) Refusing to accept the conventional wisdom that the earth was flat, Christopher Columbus's effort was tireless in pressing for royal support for a westward voyage to Asia; he endured several rejections before the securing of
It was Columbus not his effort who refused to accept wisdom.