The rotational speed of the turbo-charger of an engine which is at full throttle at low altitude is:

The correct understanding of the rotational speed of a turbocharger at full throttle and low altitude is that it operates between minimum and maximum values. At full throttle, the engine is demanding increased airflow to support combustion, and the turbocharger spins faster to meet this demand. However, the speed is not simply at maximum due to various factors such as the engine's design, boost control mechanisms, and limits to avoid overspeed situations that could damage the turbocharger.

In addition, the turbocharger has operational limits defined by its design specifications, so while it aims to reach higher speeds during full throttle conditions, it operates within a range of efficiency and safety. This balanced speed ensures optimal performance without risking mechanical failure, thus emphasizing that the rotational speed is indeed maintained between minimum and maximum thresholds for effective operation.

Other options may imply situations that don't accurately reflect the nature of turbocharging technology in these conditions. For instance, stating it would be at maximum does not account for the necessary limits and control mechanisms in place that prevent overspinning. Similarly, suggesting it is controlled by A.B.C. (which may refer to an Automatic Boost Control or similar system) implies a more complex interaction than simply recognizing that it operates within a set range of speeds. Lastly, asserting it is