GMAT Critical Reasoning (CR) | Re: Lyme disease is caused by a bacterium transmitted to humans

This question is a tricky one. Let us begin by first understanding what the question is asking.

"Which of the following would it be most important to ascertain in evaluating the argument?"
In other words, the answer to which of the following questions would be the most useful in determining whether or not the author's argument is logical.

In order to answer this question, we must first understand the author's logic.

The argument can be simplified asfollows:

[*] Lyme disease is transferred