Hi amit! I see why in this particular instance you might think of "because" as a sufficient condition indicator. But I would caution against thinking about "because" (or its close synonyms on the LSAT: "since" or "for") that way. Those are all certainly "premise" indicators, and often they can indicate a Causal relationship, but they're not enough to always necessarily create a conditional relationship. Take my Beatles inspired example: "I'm crying because the sky is blue". It wouldn't really be accurate to diagram that as: Sky is blue
I cry. Why? Well we don't know that every time the sky is blue I cry. In other words "because" isn't itself "sufficient" (sorry!) to create a sufficient/necessary relationship .
So in Fremont's statement there really isn't a sufficient or necessary indicator. In fact, there isn't really one in this whole stimulus; the best one I can point to would be the word "guarantee" in Galindo's second sentence. "Guarantee" can create a sufficient condition (for example: "A degree guarantees happiness". Degree
happiness.) Here, since Galindo is saying that it's NOT a guarantee, that means he's saying a background in the oil industry is NOT a sufficient condition for success. But Fremont wasn't saying that an oil background always guarantees success. Instead, Fremont seemed to be suggesting that it's something that's necessary, not sufficient, for success. So that's why (C) is our answer.
This question is a good example of why our table of Sufficient/Necessary indicators is not the end all be all of conditionals. Those words are a great starting point, but they don't cover every conditional. We want to be comfortable recognizing whenever an argument creates a sufficient/necessary relationship even without using one of those indicators.
Hope that helps!