一根均匀的米尺，质量为0.2kg,放在水平桌面上，它与桌面间的动摩擦因数为0.16，长度露在桌外，现有一水平拉力沿着米尺方向作用在米尺上作用1s，为使米尺能从桌边落下，外力F至少应为多少?

Most IP layer-based proxy mechanisms, such as network address translation (NAT), only support uni-directional proxy, from the internal network to external network (the Internet). The proxy establishes the communication channel by (86) IP addresses. The IP addresses must be (87) . These proxy mechanisms prevent applications that must establish return data channels from establishing their data channels, such as, multimedia applications. IP layer-based proxy mechanisms need additional software (88) for each application that uses (89) channels. SOCKS identifies communication targets through domain names, overcoming the restriction of using private IP addresses. SOCKS can use domain names to establish communication between separate LANs, with (90) IP addresses.

A．routable

B．locatable

C．path-selected

D．road-defined