Ductile cast iron___________________?

A. contains 1.7 to 3.5% carbon in free state and is obtained by the slow cooling of molten cast iron
B. is also known as chilled cast iron and is obtained by cooling rapidly. It is almost unmachinable
C. is produced by annealing process. It is soft, tough and easily machined metal
D. is produced by small additions of magnesium (or creium) in the ladle. Graphite is in nodular or spheroidal form and is well dispersed throughout the material
E. none of the above