I've found this sentence in a lesson about ordering food:
プラス５０円でキャラメルラテかカフェラテがお選び頂けますが。
A Starbucks employee says this to a customer. The meaning should be "If you pay 50 extra yen, you can get Caramel Latte or Cafe Latte".
Why is there が after カフェラテ ? I would expect を since カフェラテ is the object of the verb 選ぶ.
I wonder if 頂けます being in potential form plays a role here. I know potential verbs use が to mark what corresponds to the object in the dictionary form. Thanks.
Indeed both are possible due to the potential form of いただく heading the verb.
That said, I think が is very slightly more natural here, because you don’t really want to focus on the customer and the fact they can choose drinks (which feels very slightly less polite), but rather the drinks and the fact they can be chosen by the customer.
I just used the passive to show that in English, but in this Japanese sentence it can be done by using 〜が on the drinks (and 〜に on the customer), resulting in a similar syntactic structure to what a passive would be in English (where the grammatical subject is the drinks and the “by ...” is the customer).
If you use 〜を on the drinks, the fact the “subject” of 選ぶ is the customer feels emphasized — even though the customer still gets marked by 〜に due to いただく, it feels like there is a missing/floating 〜が which marks the customers somewhere lower down in the syntax tree (even though there isn’t?). Either way this arrangement doesn’t feel as polite/distant to me. It feels more like it’s highlighting the customer’s volition.
That all said “〜をお選びいただけます” is a perfectly valid form and this is all a bit too subtle to be certain about...
Your suspicion is entirely correct. The が marks the potential verb.
I think I would personally view お選びいただけます as a single (albeit compounded) verb, just as a I would view 選んでもらえる (which holds the same meaning) as a single (but again compounded) verb, so maybe that's a helpful way to think about this sort of construction taking が?
That all said, the use of が alongside potential verbs is not all that simple, and some people use を, sometimes depending on a nuance of what you want to say. There's a post on that here: https://japanese.stackexchange.com/a/614/33435
Hope that helps!
