下列各式中，正确的是（　　）

东晋南朝时期，江南经济迅速发展的原因有（      ）

①南方比较安定 

②北方人口大量南下　

③南方自然条件优越　

④南北方人民共同开发

1929～1933年，席卷整个资本主义世界的经济危机爆发于（     ）

    Each year thousands of____ (explore) and tourists visit the polar regions of the Arctic and Antarctica. But the increasing number of people travelling to the ends of the Earth' can have a negative effect____ fragile ecosystems. Should tourists____(allow) to visit polar regions?

    About 40,000 tourists visit Antarctica each year, More than five million travel to the Arctic and sub-Arctic. Transporting tourists to the regions ____(increase) ship and airplane traffic, adding to the risk of pollution, oil spills, and other ____(environment) damage. Because the places where wildlife is accessible ____(be) few in numbers, tourist traffic can become concentrated in specific areas,____ (put) Arctic vegetation at risk.

    Others say that access____ these very special parts of the world should not be restricted to only researches and scientist. Polar tourism allows people to develop deep personal connections with polar regions. “Those ____travel to the Arctic or Antarctica often become cheer leaders for supporting those places” Jim Sano, vice president for travel and____(conserve) at World Wildlife Fund, told TFK.

材料一　王者之制禄爵，公、侯、伯、子、男，凡五等。……天子之田方千里，公侯田方百里，伯七十里，子男五十里，……天子之县内 诸侯，禄也；外诸侯，嗣也。

                                           ――——摘自《礼记•王制篇》

材料二　天子适诸侯，曰巡狩；巡狩者，巡所守也。诸侯朝天子，曰述职；述职者，述所职也。无非事者，……一不朝则贬其爵，再不朝则削卿地，三不朝则六师移之。

                                              ――——摘自《孟子•告子》

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