Answer:
B. marginal analysis
Explanation:
"choosing a little more or a little less of a good." This part really points you to the answer.
Say you produce 10 cars, marginal cost answers the question of ¿how much costs to produce the eleventh car?
This also answers the question price and the paradox of the diamond and the water.
Normally water costs little and is a vital necessity, and diamonds costs a lot and you can live without it. If you are in a desert and no water is around I bet you'll pay a few diamonds for a bottle of water.
That's because of marginal utility, when you are thirsty the first bottle of water worths a lot, once you drink it, the second bottle worths less than the previous one, and so on.