You want the CASA answer, or the real life answer - both come with plenty of wiggle room ... it is a pity that there isn't a closer match.
My guess would be CASA want you to say rime ice, because the drops are small ... but I seem to remember they were obsessed with temperature. What does the Met "blue book" say? (CASA normally want someone else to make their decision.)
My guess of the real-life answer would be none, often don't see ice collecting until a degree or two below zero. But some clouds want to make ice, and others just don't, even though conditions are apparently perfect for crustiness.