九、 完成句子(5小题, 每小题1分, 计5分):根据汉语提示，将英语句子补充完整。

　　76.这张桌子太重我搬不动。

　　The desk is _________ _________ for me _________ _________ .

　　77.他们昨天在晚会上玩得很开心。

　　They _________ _________ _________ _________ at the party yesterday.

　　78.莫扎特4岁时开始写曲子。

　　Mozart started _________ _________ when he was four years old.

　　79.当我出去的时候我看见他们在踢足球。

　　I _________ _________ _________ football when I went out.

　　80.The boy began to go to school _________ _________ _________ _________ .(在.他7岁时)