下列单词中,划线部分发音不同的一个是 .
The boy looked ______ because he didn’t pass his maths exam.
Miss Brown, we ______ cleaning our classroom. Can we go home now?
The stories ______ were written by Mark Twain are often humorous.
The weather forecast says that ______ another storm tomorrow.
Emma looked after her pet dog ______ of all her friends.