In PN junction diode how does the majority electrons that flow from n--p leave behind an immobile positive charge as they are free electrons already ? since on doping we already got free electrons in n type

This is what i found “in a gas turbine engine, the combustor or combustion chamber is fed high pressure air by the compression system. early gas turbine engines used a single chamber known as a can type combustor. today three main configurations exist: can, annular and cannular (also referred to as can-annular tubo-annular).” i hope this you for what your looking for. can you plz mark me brainliest?

It is d, all the other ones say incorrect answer .