Academic Settings / Attendance Settings / Attendance Taking / Attendance for Subjects / Preselected Absence Category
This setting allows you to choose an Absence Category to be pre-selected as a default absence category when the end user marks a Student as absent.
The end user is given the option to select another category if required.
Setting -> Active -> Not Known reason (Figure 1)
Figure 1
Setting -> Active -> Sick (Doctor Permission) (Figure 2)
Figure 2