During the run-up at a high-elevation airport, a pilot notes a slight engine roughness that is not affected by the magneto check but grows worse during the carburetor heat check.
Under these circumstances, what would be the most logical initial action?

A. Check the results obtained with a leaner setting of the mixture.
B. Taxi back to the flight line for a maintenance check.
C. Reduce manifold pressure to control detonation.

A). Check the results obtained with a leaner setting of the mixture.

Explanation:

Under the explained circumstances, the most logical initial action would be:

A. Check the results obtained with a leaner setting of the mixture.

Explanation:

Check the results obtained with a leaner setting of the mixture, as it has been enriched by the carburetor-heated air causing engine roughness at that high altitude.

Answer b is wrong because the pilot should first try the runup with a leaner mixture and answer c is not correct because detonation is the result of a mixture that is to lean.

answer:

the correct answer is d