Etiquette

What is the proper response to the following situation? You've started a new romantic relationship but it has a surprising twist. Each time you and your new squeeze are intimately exploring each other, an ex from the past has an exquisite sense of timing, calling with his/her unique ring tone at just the, er, right moment. Is the proper response to:

a) laugh hysterically
b) answer the phone and tell the ex what a fabulous time
he/she is missing
c) admit the mood is lost and go find a good book to read
d) other...