Concept:Periodic maintenance means servicing a tractor at fixed scheduled intervals, not after every single use.
Explanation:Routine maintenance tasks happen daily or before each use.
Checking radiator water is a daily pre-operation check.
Checking tyre pressure is also a routine pre-operation check.
Cleaning after use is daily care, done immediately after the tractor is used.
These three activities are not classified as periodic maintenance.
Changing engine oil is based on the number of working hours or a set service timetable.
This makes engine oil change a scheduled or periodic maintenance activity.
Regular oil changes also protect the engine from wear and overheating over time.
Among the given options, only this task requires planned servicing intervals.
Answer:C. Changing of engine oil