Is it permissible to take off with a configuration of M/6/6?

Taking off with a configuration of M/6/6 is permissible if two engines are operational. This means that as long as two of the engines are functioning correctly, the aircraft can safely conduct a takeoff.

In various aviation contexts, particularly for multiengine aircraft, regulations often allow for takeoff with fewer than the maximum number of engines if certain conditions are met, including operational engines and the aircraft's weight limitations. The understanding here is rooted in the principles of flight safety and redundancy; as long as there are enough operational engines to maintain control and performance, the aircraft can be deemed safe for takeoff.

The other options suggest restrictions that do not align with the operational norms of multiengine aircraft. For example, needing a minimum of three engines or specifying a single operational engine would hinder the aircraft's capability to operate under its designed parameters. Additionally, the notion that weight alone dictates the ability to take off is an oversimplification, as engine operability is also a crucial factor alongside weight considerations.