Bonjour John,

"à laquelle" and "à qui" are both correct answers as per the lesson content.

As a multiple choice question, "à qui" isn't given as an option here but "dont / à quoi / auquel / à laquelle". However, "à qui" is indeed a correct option if you were asked to write down your answer. ;-)

I hope this is helpful.

Bonne journée !