下列各组物质中全部都属于纯净物的是                                          

In general , it is failure which encourages us to work harder that __________ leads to success .

一个数的因数和倍数的个数都是有限的。（    ）

针对“南中国海争端”问题，淮安市某高中生运用所学知识在网络博客中发表文章《南沙群岛--中国的主权》，阐述和论证南沙群岛属于中国领土有其历史和法律依据。该中学生的行为体现了公民（   ）
①行使政治自由权           ②履行维护国家利益的义务
③履行维护国家统一的义务   ④享有监督权

The world considers Japan to be the best prepared to deal with an earthquake emergency. _______, the March 11 earthquake, followed by a strong tsunami minutes later, still left thousands of people dead.