whether vs either


The key for the following question is “A. whether”. Could anyone please tell me why “either” doesn’t work? Many thanks.

Question: Customers who purchase concert tickets will be charged a service fee ( )they pay by cash or by credit card. a. whether b. either c. even d. despite

The answer key is correct.

‘Whether’ indicates that a statement applies whichever of the alternatives mentioned (payment by cash or payment by credit card) is the case. There will be a service fee regardless of which method of payment is used.
Another example:
I’m going whether you like it or not.

Thank you very much, Beeesneees. :slight_smile: