When using a font stack to declare the font family, in what

The first value is the first choice, followed by alternative options, ordered by preference. The last option should be a generic font.
The first value is the first choice. The order of the alternative options does not matter. It depends on what is available on the user’s computer.
The first value is the first choice, and must be followed by at least one alternative option before adding the generic font.
The first value is the first choice, followed by a maximum of three alternatives.

When using a font stack to declare the font family, in what order should the values appear?