内容是这样的：Tom邀请LiPing参加他这个星期天的生日聚会,但LiPing的父母出差要到下个月才回来,奶奶又卧病在床,需要人照顾,再说英语考试即将来临,因此,无法前去参加宴会,LiPing感到很抱歉,

dear tom,
i'm very happy that you invite me to your birthday party this week,but i am very sorry that i cannot make it.my parents went out for work and can only return next month,but my grandmother is sick in bed so i must take care of her.i also have piano lesson this week and lots of homework to do.besides,our english exam is coming and i must study for it.therefore i will not be able to go for your party,i am terribly sorry.happy birthday!
regardsli ping