「従兄弟の車を運転____、すごくスピードが出て、楽しかったよ！」
Correct answer させてもらったら。 I feel as though I understand the principle behind this grammar topic (To have the honor of doing, To take the liberty of doing, To do (polite, formal)), but this specific question example makes use of the conditional/hypothetical form 〜たら / 〜だら. I once read somewhere that this form can also be used to make things more polite/less assuming.
(a) Is that also how it’s being used in this example?
(b) Does anyone have more to add to this topic? Or perhaps it’s already covered in another bunpro grammar example
(c) For those that get the chance to speak Japanese daily in a workplace setting, do you find yourselves using this often?