Researches have noted that panda bears that have given birth

I completely agree to this explanation, but I would like to add a little more to it. Let me explain:

In causation, there are 4 cases:
1) X causes Y
2) Y causes X
3) Z causes X & Y
4) X & Y are not co-related.

Let's say Panda giving birth to live young = X, Longlife = Y. The author has concluded that X causes Y.

Now, in order to support this conclusion, any one of the below possibilities will be required:
i) something that directly supports 1) i.e. X causes Y, OR [
ii) something that negates 2) i.e. indicating Y didn't cause X, AND
iii) something that negates 3) i.e. indicating Z didn't cause X & Y, AND
iv) something that negates 4) i.e. indicating X & Y are correlated ]


The revised option C (with the NOT) i.e. "Pandas that are already likely to live longer are also NOT more likely to give birth to live young" is basically the negation of case 2), or in other words, possibility ii), which is absolutely correct. One may argue that either ii), iii) and iv) must be combined together or i) standalone be chosen in order to conclude the author's conclusion. But conclusion is not what is asked here. The question is asking about assumption, and ii) is one of the assumptions. Hence ii), i.e option C (with the NOT), is one of the CORRECT answers. Other correct answers could also have been assumptions that supported i) or iii) or iv). Those assumptions are not mentioned in the answer choices though.

I noticed some people chose option A. I found option A very tricky! Initially (when NOT wasn't there in option C), even I felt that option A was directly supporting case 1) [i.e. possibility i)], and hence was the correct answer. But I later thought that even if predators do not kill pandas that give birth, still that doesn't guarantee long life. Pandas may die early for some other reason. Option A) neither negates all possibilities of an early death, nor indicates any biological change in the pandas (e.g. release of some hormones) that, in general, would result in healthier life and /or longer life span. Hence A is incorrect.

Please let me know if anyone disagrees with the way I am thinking. Any feedback will help me correct/improve my way of thinking.
By the way, in case you agree, feel free to give kudos. That won't hurt!