How is this sentence correctly written?

last week, the twin's parents threw them a sensational birthday party.

a: the twins' parents
b: the twins's parents
c: the twins parents'
d: correct as is

The correct answer would be 'A: the twins' parents' because there's more than one twin, and it's possessive. 

Another example would be, if you had two burgers and they both had ketchup you might say something like,
The burgers' ketchup.

Hope this helped! If you have anymore questions or don't understand, please comment or DM me. :)

What are the options or is it in the question above