句型：1) i have to ask for leave of absence.2) your kind permission would be greatly appreciated.dear sir,because of an attack of a bad cold with a fever, i shall not be able to attend classes today. i have to ask for leave of absence.enclosed is a medical certificate issued by the school clinic.your kind permission will be greatly appreciated. yours respectfully,kelly smithl useful expressions1) i would appreciate it very much if you could give me one day’s leave.