Jumping out of airplane at a height of 5000 kilometers is unforgettable experience.A. a

问题补充：

Jumping out of airplane at a height of 5000 kilometers is unforgettable experience.

A. an ; a

B. an ; an

C. an ; /

D. a ; an

答案：

A. an ; a

(答案→)B. an ; an

C. an ; /

D. a ; an

解析：考查冠词用法。修饰可数名词用不定冠词a/an；这里的“一架飞机”是泛指，airplane首字母发音是元音，故用an，排除D；experience指“经历”时，是可数名词，unforgettable首字母发音是元音，用an修饰，排除A、C，故选B。