Closed runways are marked __ and closed taxiways are marked by _.

A) Closed runways are marked with large yellow crosses, and closed taxiways are marked with yellow crosses.
B) Closed runways are marked with red lights, and closed taxiways are marked with green lights.
C) Closed runways are marked with white flags, and closed taxiways are marked with orange flags.
D) Closed runways are marked with black and white stripes, and closed taxiways are marked with blue and white stripes.

Closed runways are marked with large yellow crosses visible from the air, while closed taxiways are also marked with yellow crosses visible on the ground. option a

Explanation:

The markings for closed runways and taxiways are important safety features in aviation. The correct markings are:

Closed runways are marked with large yellow crosses, which can be seen from the air by pilots.
Closed taxiways are marked by yellow crosses as well, but these are designed to be recognized on the ground by taxiing aircraft.

The other options listed include incorrect color markings or symbols that are not standard in the aviation industry for indicating closed runways and taxiways. Safety in aviation is paramount, and the correct signage is necessary to prevent accidents on the airfield.