Question ATPL - Airline Transport Pilot license - Performance

Under which condition should you fly considerably lower (4 000 ft or more) than the optimum altitude ? - ATPL

If the maximum altitude is below the optimum altitude.

If at the lower altitude either considerably less headwind or considerably more tailwind can be expected.

If at the lower altitude either more headwind or less tailwind can be expected.

If the temperature is lower at the low altitude (high altitude inversion).