Final answer:
The correct statement concerning volcanic ash is that even a thin layer of volcanic ash on the runway can be detrimental to braking action.
Step-by-step explanation:
The correct statement concerning volcanic ash is b. Even a thin layer of volcanic ash on the runway can be detrimental to braking action.
Volcanic ash is finely fragmented material that is less than 2 mm in diameter and is created during volcanic eruptions. Although volcanic ash is not as abrasive as sand, it can still cause significant damage to aircraft and infrastructure due to its fine particles that can penetrate mechanical systems and engines. Runways covered in volcanic ash can reduce braking action, posing a safety risk for airplane landings and takeoffs.
Therefore, option b is the correct statement.