Answer choice A: "if and only if" construction?

I'm just wondering if answer A has an implied "if and/but only if" construciton. "If the restaurant is full, the parking lot will be full, and if the parking lot is full, the restaurant is full" Diagrammed separately, it's RF --> PLF (not PLF --> not RF) PLF --> RF (not RF --> not PLF) It seems like we could diagram it as follows: RF <-----> PLF So far, I haven't seen "if and only if" in any questions, and it wasn't mentioned in the videos or in any of the threads.