Sky moral duty is to attack on the penultimate climb... the classic off the shelf "last 5 Km attack" is not going to yield the 81 seconds Froome needs. Could be a good day...
Quintana doesn't need to risk blowing, he just needs to follow.
Let's be honest, they won't do anything until 2k to go, then Froome will attack, Quintana will know he's got the race won and limit him to 30 seconds gain, if that
100m into the stage and no GC action yet