The risk to the exporter in open account trading is that by surrendering the shipping documents to the importer, he（）before he has obtained payment for them.

A．is in control of the goods

B．loses control of the goods

C．retains control of the goods

D．gives up control of the goods

经检查决定剖腹手术，术前准备中最关键的措施是

A．禁食

B．插胃管，胃肠减压

C．补液，输血

D．应用抗生素