Last night he wrote a ( ) letter to his friend.

问题描述:

Last night he wrote a ( ) letter to his friend.
填100-word 还是 100 words

100-word 一百字的 复合形容词
在复合形容词中,可数名词必须以单数形式出现
1,500-mile journey 一千五百英里的行程
a ten-year-old boy 一个十岁的男孩