Question

Every morning Mr.Smith takes a______to his office.

Every morning Mr.Smith takes a______to his office.
A .20 minutes' walk B.20 minute's walk C.20-minutes walk D.20-minute walk

Answer 1

你好。答案是D
20-minute是形容词，後面加名词。walk是名词，可数名词的单数，所以，前面有 a 。
记住：
a 20-minute walk
== 20 minutes' walk
== a walk lasting 20 minutes

Answer 2

选D 数字+连字符+名词单数=所对应的形容词 是一种常见用法 译为“20分钟的路程”。类似的还有a 10-year-old boy一个十岁的男孩 。 特别注意：这种词为形容词，而且词中名词的复数形式要变为单数。