Student or Learner
I don't understand how this question could mean an invalidation of the author's point.
"Which of the following findings would most compromise the author's conclusions.."
One of the answer solution says "This response would invalidate the author's hypothesis."
It seems to me that I'm confused on what compromise means. I see it as an agreement on both sides.
However, it can also mean to reduce the quality or value:
1. a. To expose or make liable to danger, suspicion, or disrepute: a secret mission that was compromised and had to be abandoned; compromise one's standing in the community.
b. To reduce in quality, value, or degree; weaken or lower.
(From The Free Dictionary)
So in your context, it means that there are some findings in the piece which make the author's conclusions appear less defensible or less correct.