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Explanation:

The three different security points are;

Initial checkup,

When you just enter the lounge of airport, a passenger and all his luggage is passed through screening to screen out any prohibited item in luggage

Identity Checkup

Before taking the bording pass, one has to for his or her individual check up, where the criminal record is checked against each person

Boarding Check up;

This is the final checking before boarding the plane, your handcarry is also screened here