题干

有人用锅煮鸡蛋,当水烧开之后,为了使鸡蛋快点烧熟,他加大火力,让水沸腾得更加剧烈些,试用科学原理分析他的做法是否合理。

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答案(点此获取答案解析)

不合理。因为当水沸腾后其温度已经达到水的沸点100℃,如果继续用大火加热,水温仍然是100℃,不能缩短鸡蛋煮熟时间,所以只需要用小火加热,让水保持沸腾就可以,这样还能节约燃料。

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阅读理解

    China is a big country, and there is no simple answer to the question “When is the best time to visit China? ” There are two best times to visit China, depending on your preference.

    October

    Things to do: hike on the Great Wall, photography tour

    Places to visit: Beijing, Xi'an, Shanghai, Guilin, Jiuzhaigou, Chengdu

The best time to go to China is early autumn (October).

    Most of China has warm temperatures, and the summer rains have stopped (apart from around HongKong and Sanya) so it's pretty dry. The autumnn colours are also amazing. It is quiet at tourist attractions for most of the month, as the summer holiday travel crowds have gone. But try to avoid October 1st -7th, which is the Chinese National Day holiday, as attractions, transport and hotels are packed with Chinese tourists and prices go up a lot.

    Late Spring (April to May)

    Things to do: appreciate flowers, Li River cruise, ethnic festivals

    Places to visit: Beijing, Xi'an, Guilin, Huangshan, GuiZhou, Zhangjiajie

    The second-best time to travel to China is probably in April and May, when the flowers are in bloom and the temperatures are warming up. In late spring, temperatures across China are getting into the 20s (℃), except the extreme northwest and northeast. While the North of China is still dry, the summer rains have already begun in the South. This could actually improve the view in the form of mountain fog in mountainous areas like the Li River and the Yellow Mountains.

    Ethnic festivals in GuiZhou are concentrated in April and May, such as the Sisters' Meal Festival. If you are interested in Miao and Dong ethnic cultures, this is a good time to visit.

    Travel prices are average: cheaper than June to October, but more expensive than the lower season from November to March.