合同对标的物交付规定不明确的，（）视为交付。

A.需要办理法定手续的，办完一定手续时

B.由出卖人送货上门的，出卖人将标的物送到指定地点，买受人验收后

C.由出卖人代邮的，出卖人办完邮寄手续后

D.标的物在订立合同之前，已为买受人所占有的，合同生效时

E.由出卖人代运的，出卖人办完托运手续后

The development of e-commerce may well bring the world into a brand new era of "electronic currency". At the moment, (51) areas in Europe, the United States and Asia have already started studying the possibility of an electronic currency. Electronic currency is not only about currency. It (52) to an entire finance system on the Net. It includes a virtual numeric currency, an electronic system of withdrawals, transfers and loans, and (53) cards of all shapes and sizes. The (54) of an electronic currency system implies the emergence of "virtual banks" and "virtual enterprises". Actually, the first virtual bank appeared in the US in 1995. (55) it is a small and insignificant bank, it represents the trend of the future. In time to come, we may even have to (56) the familiar paper currency.

As the Net pushes the economy (57) rapidly, the economy is also bringing the Net market forward, resulting in the Internet itself becoming the world’s largest emerging market. Of course, this is just the beginning. Although there are many companies which made huge profits (58) in the Internet market, they tend to be small companies. To date, most companies are making losses. The competition in the knowledge-based economy will also be more (59) This will definitely promote (60) and more efficient cooperation.

51().

A.developing 

B.building 

C.built 

D.developed