Explanation

Identify the contrast: The sentence tells us two things about the physicist:

-She respected her former supervisor so deeply that she declined a prestigious position rather than compete with his laboratory for funding.
-However, she publicly challenged several of his scientific findings in published rebuttals.

The word “nonetheless” signals that her respect had a limit. Although she admired him greatly, she was willing to disagree with him scientifically.

Understand the blank: The phrase “her esteem for him nonetheless fell short of _______” means that her respect did not reach the level of something even more intense or absolute.

C. unalloyed reverence means pure, unqualified admiration and profound respect.

Her willingness to publish rebuttals demonstrates that she did not regard her supervisor as infallible.

Eliminate the other choices

-A. perfunctory cordiality - superficial politeness; far weaker than the esteem already described.
-B. requited ardor - passionate affection that is reciprocated; inappropriate in this context.
-C. unalloyed reverence - absolute, unquestioning admiration; fits the contrast.
-D. unswerving fealty - unwavering loyalty or allegiance; plausible, but less directly connected to the contrast between esteem and scientific criticism.
-E. public avowal - an open declaration; does not express a degree of respect.

Answer: C