dear mr/ms jiang
i was unable to come to 1st and 2nd period today.due to the rain yesterday, i was wet and had temperature at night. the doctor adviced me to rest for several days and after my recovery, i will attend school as soon as possible.
i am sincerely sorry about the inconvenience. however, i would like to have your permission. also, afterwards i would phone you and there's the certificate by the doctor.
october 21st 20xx