Thank you very much for inviting me to your birthday party. I'd love to go but I can't . My parents are away on business. They won't be back until next month. And my grandma is sick in bed so she needs looking after. On top of that, the English test is just around the corner so I have to study for it. All in all, I'm afraid I won't be able to make it to your party. I'm terribly sorry. But thanks again for the invitation.
Dear Tom, thanks you very much for inviting me to your birthday party.I'd love to go but I can't.My parents have travelled on business and will not come back until next month.On the other hand, my grandma is ill in bed,which is needed to be taken care of. at the same time, the english exam is coming soon,so it is a pity that I can't take part in your birthday party.