July 13th
Dear Miss Smith,
I am very sorry that i am unable to go to school today due to a bad stomachache. I have enclosed a certificate from my doctor and ask you for sick leave of four days.
I should be very obliged if you grant my leave. Considering the lessons missed during my absence, I will try my best to make them up.
yours respectfully,
Kangkang
Encl: doctor's certificate for sick leave