Thank you very much for (invite-inviting) me to your birthday party (in-on) Saturday morning.I'd like to come (and_but) I have to go to my hometown to see my grandparents. They (were-are) very old and unluckily they are not in(去掉 a ）good health recently. My mother has already made a telephone call to them and promised（加to） visit them with me this Saturday .My mother saidwe （will-would） stay at my grandparents' the whole weekend. So I'm （real——really） sorry I can't attend your party. I hope you will understand all （this-these）. Here I wish you a lot （of) fun on your birthday and much happy returns of the day.