New York London are two of the largest cities in the world.A. Either; or 　 B. Both; and

问题补充：

New York London are two of the largest cities in the world.

A. Either; or

B. Both; and

C. Neither; nor

D. Not only; but also

答案：

A. Either; or

(答案→)B. Both; and

C. Neither; nor

D. Not only; but also

解析：

根据谓语动词判断，应该是both …and..结构。其它几个都是就近一致原则，该用单数。