依据《招标投标法》，下列能使招标行为发生法律效力，一旦有一方违约，应承担违约责任的行为是( )。

A．招标人与中标人签订书面合同

B．招标人向中标人发出中标通知书

C．投标人收到招标人发出的中标通知书

D．评标委员会在投标人中选出中标者

Which of the following statements about speculators and hedgers in the futures market is TRUE()

A. Hedging can allow a business to guard against a price increase in a commodity without sacrificing profit if the commodity price decreases. 

B. Hedgers guard against market price changes that would cause a reduction in their operating profit. 

C. A speculator would use futures to take a short position in a commodity if its price is expected to increase.