What signal will an officer in their vehicle use to indicate that the road is again open to traffic?

A)A red flag.
B)A green flag.Correct
C)A red light.
To indicate that the road is open again to traffic, a green flag will be used.
A red flag indicates that, from the moment the vehicle carrying it passes, the road is temporarily closed to traffic of all vehicles and users, except for those accompanied or escorted by the agents of the authority responsible for the regulation, management and control of traffic.
The yellow flag indicates to other drivers and users the need to pay extra attention or the proximity of a danger. This flag may also be used by authorised auxiliary personnel performing order, control or safety duties during the development of cycling races or any other activity, sporting or otherwise, on roads subject to the legislation on traffic, motor vehicle circulation and road safety.