感谢你邀请我参加你的晚宴，但是我很抱歉我不能去，因为那天我有一个重要的会议。
选项：

A:Thank you for inviting me to you dinner party. And I shall be happy to attend it.
B:Thank you for inviting me to your dinner party. But I regret that I will not able to go there as I have an important meeting that day.
C:Thank you for inviting me to you dinner party. And I will go there even if I have an important meeting that day.