Can a passenger car displaying this disabled person sign use an HOV lane (carril VAO)?

A)No, unless they have special authorisation from the road authority.
B)Only if occupied by two or more people.
C)Yes, even when occupied only by the driver.Correct
As a general rule, the BUS-HOV lane may be used by two- or three-wheeled motorcycles, passenger cars, buses with a maximum authorised mass exceeding 3,500 kilograms, articulated buses, and adaptable mixed-use vehicles with the number of occupants set per section. All other vehicles and vehicle combinations are prohibited from using it, including passenger cars with trailers, cycles, and mopeds. However, the following may also use it even when occupied only by the driver: - Authorised vehicle types displaying the V-15 sign (reduced mobility badge). - Two- or three-wheeled motorcycles. - Buses with a maximum authorised mass exceeding 3,500 kilograms and articulated buses. - Vehicles classified as taxis under the usage criteria of Annex II of the General Vehicle Regulations, equipped with an exterior light module and a valid taxi licence. - Police, fire-fighting, civil protection, rescue, and emergency medical service vehicles on emergency duty, and road maintenance and infrastructure teams. - Passenger cars displaying the V-25 environmental badge sign classified in the Vehicle Register of the Autonomous Body Central Traffic Headquarters as '0 emissions'. - Passenger cars displaying the V-25 environmental badge sign classified in the Vehicle Register of the Autonomous Body Central Traffic Headquarters as 'ECO', 'C', or 'B', only when the variable message panels at the HOV lane access points indicate this.