One rune? Well, since most of the ones Cela'd choose had already been selected, Cel decided to be literal.
She pulled her choice out and raised her hand.
"I'd choose Isa and freeeeeeze the water so that you won't drown, professor. At least it would allow you to freeze the situation so that you could stop and reevaluate where you are and have time to think of a really good plan without having to rush." She cheerfully answered and snacked on candy.