53. Global warming is caused by many factors. (1). Many developing countries are becoming industrialized. (2). The number of cars on our streets is growing. (3). Cheap air travel is allowing more people to fly.
全球变暖是由很多因素造成的。比如，很多发展中国家的工业化，汽车数量的增加，廉价航空载送越来越多的人。
54. Global warming will have a significant impact on our planet. Rising temperature will cause melting of the polar ice caps, and then sea levels will rise. At the same time. we can expect more extreme weather conditions; for example, flooding and drought may become more common.
全球变暖对我们的星球将会有显著的影响。气温的升高将会导致极地冰冠的融化，从而带来海平面的上升。同时，越来越多的极端天气会发生，比如，洪水和干旱会变得更常见。
