With a determiner:
(1)Salt is ____ essential ingredient in all kinds of food. (2)-Which of the two buses shall I take to the airport? -You can take ____ one.
【正确答案】：an; either
【题目解析】：【考点点击】本题考查限定词。【要点透析】 essential中第一个音节是元音,所以用an修饰。表示两者中的任一个,需用 eithero
