Which casting method makes a pattern of the same shape as the product from wax, coats it with several layers of refractory slurry and hardens them, then heats it to melt out the wax and pours melt into the resulting mold?

Answer: C. Investment casting

In investment casting (the lost-wax process) the pattern is melted out, so the mold does not have to be split to remove it, and complex shapes can be made with good dimensional accuracy and smooth surfaces. The refractory mold withstands high temperatures, so the method is also used for precision parts in Ni-based superalloys, such as jet-engine turbine blades, and directionally solidified and single-crystal blades are made this way as well. Die casting injects melts of aluminum, magnesium and the like into metal dies under high pressure; it is highly productive and suited to thin-walled parts, but not to high-melting steels. Sand casting makes a sand mold from a pattern such as a wooden one and then withdraws the pattern; it can make large parts, but the surface is rough.