When moving the mixture control on a normally operating engine into the idle cutoff position, engine RPM should?

When the mixture control on a normally operating engine is moved into the idle cutoff position, the mixture of fuel and air becomes excessively lean, which ultimately affects combustion. As the engine transitions to a leaner mixture, it often responds with a slight increase in RPM due to the change in fuel delivery before it begins to starve for fuel. This phenomenon occurs because the engine may momentarily adjust to the lean condition before the combustion process is significantly affected.

After this brief moment where the RPM increases slightly, the lack of adequate fuel leads the engine RPM to drop as it can no longer sustain the combustion process efficiently. Thus, this option accurately describes the expected behavior of the engine RPM, making it the correct answer.