13. In western North America, _____ form the Great Divide, which separates the areas from which waters flow either eastward to the Atlantic or westward to the Pacific.
(A) the Rocky Mountains
(B) where the Rocky Mountains
(C) the Rocky Mountains in which
(D) there are the Rocky Mountains
Ans:A
why A?我看不到主要動詞ㄋㄟ
所以偶選D