GRE Vocabulary Builder

Answer: Choice (D) is correct.

Zenith and summit are both words that refer to the highest point of something, like a mountaintop. Therefore, look for the pair of words that are synonyms. Apex also means the highest point, but nadir means the lowest point, so eliminate that choice. Yen and yang is a Chinese term that refers to dualities (such as light and dark) that co-exist. Since these are antonyms, eliminate choice C. Vale and gorge both refer to low points, such as a valley, so choice D is the most appropriate choice.