Given the statement If there is an accident then the traffic is backed up. Which of these contrapositive of this statement.

Accidents always makes the traffic back up.
If there is no accident then the traffic is not backed up.
If the traffic is not backed up then there is not an accident.
If the traffic is backed up then there is an accident

If the traffic is not backed up then there is not an accident.

The contrapositive of the statement "If there is an accident then the traffic is backed up" is "If the traffic is not backed up then there is not an accident."