Dear Ann,
Thank you very much for inviting me to your home for lunch. But I will take an important exam the day after tomorrow. I must work hard on it to pass it. I'm so sorry that I cannot come to your lunch. Thank you again for your inviting.
Dear Ann,
Thank you very much for inviting me to your home for lunch. But I will take an important exam the day after tomorrow. I must work hard on it to pass it. I'm so sorry that I cannot come to your lunch. Thank you again for your inviting.