请什么假?理由?非常感谢，因为导师要求我去出野外采集数据，故无法上英语写作课（外教的课）。Dear <外教名字>,I am writing to ask for your approval for my leave on .My tutor has asked me to go out with him on that day to collect raw data. I apologize that I will not be able to attend the class as this project is so important for me that I could not miss it.Thank you for your understanding. Your earliest response will be highly appreciated.Kind regards,