Which of the following makes the enigma encryption scheme a mechanical version of a poly$-$alphabet cipher?

Group of answer choices

The number of possible keys, or initial rotor settings.

The fact that the rotor settings changed each time a character was entered.

The fact that a simple test message was sent at the start of each day.

The fact that the keys, or initial rotor settings, did not need to be exchanged.

The fact that the initial rotor settings changed each day.