The correct answer is: C. in the bottle was not enough
The sentence is about the amount of water in a bottle. The first part of the sentence, “Little water,” tells us that there is not much water. The second part of the sentence, “that was left,” tells us that the water is not all there is. The third part of the sentence, “in the bottle,” tells us where the water is. The fourth part of the sentence, “was not enough,” tells us that the water is not enough. The fifth part of the sentence, “to quench the thirst of two persons,” tells us what the water is not enough for.
The sentence is grammatically correct and makes sense. The only part of the sentence that is not necessary is the phrase “in the bottle.” The sentence would be just as clear and concise without that phrase.
Here is the sentence with the phrase “in the bottle” removed:
Little water that was left was not enough to quench the thirst of two persons.
This sentence is still grammatically correct and makes sense. It is also more concise and to the point.