I often write letter to my pen friend.
A. a eight hundred words
B. eight hundred words
C. an eight hundred word
D. an eight-hundred-word
网友回答
A. a eight hundred words
B. eight hundred words
C. an eight hundred word
(答案→)D. an eight-hundred-word
解析：本题考查的是复合形容词的用法。复合形容词中间有连字符，之间的名词用单数形式。句意：我经常给我的笔友写八百字的信。八百字的信，应表达为an eight-hundred-word letter，故选D。