(2013·东北三校4月联考)—Car prices have been going down sharply in the last 20 years.

—It's not surprising because the law of market ________ the price of a product.

A．is controlling

B．controls

C．has controlled

D．controlled

有效用人除了公开、公平、考核竞争、全面、择优、量才适用、效率等原则外，还必须遵循（）原则。