When he looked up，he suddenly found himself ______by a group of teenagers，____looked at him anxiously.

A．to be surrounded；which

B．surrounded；who

C．be surrounded；who

D．having been surrounded；which

关于接受生效的时间，各国法律有不同的规定，其中( )采用“投邮生效”的原则。

A．英美法

B．大陆法

C．《联合国国际货物销售合同公约》

D．我国的《合同法》