用方框中所给单词的适当形式填空，每个单词限用一次。（每空限填一词）

fisherman     prefer     usual   success    easy

Tom ______classical music to pop music in his free time.
June 5^th is an ________ day. It is World Environment Day.
The __________ were very happy because they catch many fish.
You can never be_______ , unless you work hard.
They can become unhappy___________ if they can’t deal with the problems.