依照河南省邮政条例的规定，用户在什么情况下可以依法拒绝签收快件？
第一代计算机
在制定调查研究计划的过程中，最为核心的环节是（）。 ["编写调查研究纲要","明确调查研究目的","制定调查研究计划","调查研究前期准备"]
常用的萃取方法有（） ["有机溶剂萃取","双水相萃取","超临界萃取","反胶束萃取"]
What is the difference between the IPv6 addresses ：：/0 and ：：/128？（） ["：：\/0 is the unspecified address， and ：：\/128 is the multicast address","：：\/0 is the unicast address， and ：：\/128 is the anycast address","：：\/0 is the unicast address， and ：：\/128 is the multicast address","：：\/0 is the anycast address， and ：：\/128 is the multicast address","：：\/0 is the default route， and ：：\/128 is the unspecified address","：：\/0 is the anycast address， and ：：\/128 is the default addre"]
神经递质
