How Is the Doneness Test Determining the "Hard Crack" Stage

How is the doneness test determining the "hard crack" stage for candy syrup temperatures described?

A) no water test; the sugar liquefies and becomes light brown
B) syrup separates into threads that are hard and brittle, but do not stick to fingers
C) syrup forms a ball that is hard enough to hold its shape, yet plastic enough to roll out
D) syrup forms a ball that flattens out between fingers