根据首字母及汉语提示，完成下列单词的拼写，使句意明确，语言通顺。
The Internet is becoming a u _____ (有用的)tool for students.
We feel it is our d _____ (责任)to help each other.
You are b _____ (勇敢的) enough to accept such a difficult job.
I'm afraid we have to c _____ ( 取消)the meeting.
Bob has many story books and he often s _____ (分享)thcm with his friends