The correct answer is C. Uranium oxide.
Yellowcake is a fine, powdery form of uranium oxide (U3O8). It is the intermediate product between uranium ore and uranium hexafluoride, which is used to produce uranium fuel for nuclear reactors. Yellowcake is a valuable commodity and is often smuggled across borders illegally.
A. A crude from of heroin is not yellowcake. Heroin is a white or brown powder that is made from morphine, which is extracted from the opium poppy.
B. A crude from of cocaine is not yellowcake. Cocaine is a white powder that is made from the leaves of the coca plant.
D. Unreformed gold is not yellowcake. Unreformed gold is a solid, yellow metal that is found in nature.