在下列各句的空格内填上一个适当的完整的单词，该词的首字母已给。
In autumn the leaves of most trees turn y________.
There’s no b________ over the river. We have to cross it by boat.
It’s best to water plants either e________ in the morning or late at night.
Many children like spending much money in b________ beautiful pencil boxes.
Before you come into the room, please k ________ at the door.

story   practice   find   notebook  but