阅读下面短文，在空白处填入一个适当的词，或填入括号中所给的单词的正确形式。

    Bill, Lisa and Peter are classmates. They're all 13 (year) old. Bill likes music. He can play guitar, but he can't play the violin. He thinks it's difficult (play) the violin. Lisa likes music, too. She (sing) English songs very well, but she can't sing Chinese songs. Peter likes sports. He can play basketball well. he can't play soccer. He says soccer is boring.