I would go with the last sentence.
The question is whether those phrases are speaking of the same person :
<span>A. her friend and former room-mate
- this is the same person, if it was two people, it'd be "and her"
B. </span><span>the winner and still champion
-again, the same person, requires singular verb
C.</span><span>The chief and foremost expert
-again, the same person: requires a singular verb and actually has a singular verb, correct answer!
</span>
Answer:
I think the most important part of the plot is change
The phrase that provides context clues for the definition of the word majority is “ More students voted for healthy lunch choices “
I would guess that it would be C. Sea Life is broader than "fish". Water pollution is much broader than both because it isn't targetting any specific topic within water pollution, and pollution is anything within pollution which is even MORE broad. (not to mention C is concerning LAKE water instead of just water)
