C is the only right answer. I've seen tons of language geeks mix up "fazed" and "phased," using the ph one for all purposes. I think most people just haven't even heard of "fazed." So, to clear it up, I'll say that if you're fazed, you're disconcerted, while if you're phased, well, you're probably getting phased OUT, because it's unlikely you're phasing through something. Maybe this started getting confused by people who know Star Trek guys carry phasers which can faze or stun?

The others:

• A features the wrong form of "lets." It should be "let's." "Lets" is a word but it would only be used if someone "lets" you do something (or it can be the plural of a shot in tennis called a let, but let's not get into that).
• B features "yea," which is also a word but does not mean the same thing as "yeah." If you take off the h, I'm afraid you have a word that rhymes with "nay," and it means the opposite; it's an antiquated way to approve. "How many say yea? How many nay?"
• D features the phrase "mean time." The way it's used here, it should be "meantime." The time in between. If you separate the words, you're talking math language, looking for the halfway point between highest and lowest times.