Which one belongs to expendable molds?

Expendable molds,Which typically are made of sand

To change the style of management that has been ______ for a century requires retraining for every position. A: elabotate B: expendable C: ethical D: prevalent

Expendable molds , which typically are made of sand, plaster, ceramics, and similar materials and generally are mixed with various binders(bonding agents) for improved properties. These materials are refractories (that is, they are capable of with standing the high temperatures of molten metals). After the casting has solidified, the mold is broken up to remove the casting.