Jack's teacher has a box of objects. He asks each student to pull out an object and identify whether it is a mixture or a pure substance. Jack pulls out a piece of iron. What is this object and why is it a mixture or a pure substance? A. A mixture, because it is only composed of one thing B. A pure substance, because there are several things making up the object C. A mixture, because there are several things making up the object D. A pure substance, because it is only composed of one thing