TOEFL® questions: 'as same as' vs 'the same than' vs 'the same as' vs 'a same one'

[Hongrose1986]

Today's typewriter keyboard is Shole's 1867 keyboard ...

1/ as same as
2/ the same than
3/ the same as
4/ a same one as

which one should i choose? why?

Please explain its function to me

[Proalyssa199]

I think people frequently use "the same as" or "the same one as".
Ex: My book is the same as yours./ I have the same book as you.