Hi Terry,
Thanks for the question, and welcome to the Forum!
This is a somewhat tricky Flaw in the Reasoning question, where the flaw itself is based on a conditional reasoning error known as a Mistaken Reversal. So let's see if we can set the argument up and then look at how the conclusion commits this mistake.
The first sentence tells us that being a good manager (GM) requires that one understand people (UP) and be able to defuse tense situations (DFT), and then, somewhat oddly, we're told the anyone able to defuse tense situations must understand people. So we can create a diagram if we want that ties all of that together:
UP
GM
+
DFT
UP
Connecting DFT to UP is an unusual step, but it essentially means that there are two ways you could know someone understands people: if they're a good manager, of if they're merely able to defuse tense situations (regardless of what kind of manager they might be).
But what we need to avoid here at all costs is the tendency to go backwards against these arrows! To say that understanding people means you can defuse tense situations or that you're a good manager, for instance, would be a mistake. Similarly, knowing someone is able to defuse tense situations and then concluding that they're a good manager would be a reversal of the terms and thus may not be true.
And that's where the error comes in. The last sentence concludes that Ishiko can defuse tense situations so she must be a good manager:
DFT
GM
That's backwards, reversing the connection between GM and DFT that we have from the first sentence.
Now we need an answer choice that describes that reversal, making sure we include the proper piece(s) involved.
Answer choice (C) gives us what we want: the confusion between a quality necessary for being a good manager (DFT is necessary in our first diagram above, GM
DFT) with a quality that guarantees (is sufficient for) being a good manager (DFT is given as sufficient in the conclusion, which is the Mistaken Reversal, DFT
GM).
That's pretty classic LSAT wording for a Mistaken Reversal, so I'm glad you've encountered it early in your prep and I hope this answer helps to better explain it
Thanks again!
Jon