Final answer:
In case of a radio failure at a controlled airport, the pilot should enter the traffic pattern and look for light signals from the control tower to land safely.
Step-by-step explanation:
If an aircraft's radio fails while attempting to land at a controlled airport, the recommended procedure is:
b) Enter the traffic pattern and observe the light signals from the control tower.
This procedure is established so that the pilot can safely alert the control tower of their situation and receive light signals that will guide them in landing without verbal communication. Trying to fix the radio while circling or performing aerobatic maneuvers to attract attention are not recommended and can be dangerous.