在下面一段文字的横线处补写恰当的语句，使整段文字语意完整连贯，内容贴切，逻辑严密。每处不超过15个字。

    光是人类的好朋友，①                           。然而，光一旦变成污染，②                           ：比如过强过滥的光、变化过于迅速的光会破坏植物的生长规律，会影响人的生理与心理正常。现在，国内不少城市还在不惜重金打造一座座“不夜城”，而这些所谓的“不夜城”恰恰是光污染的重灾区。看美国大片，总以为纽约是一座不眠的美丽城市。其实纽约对夜间强光和霓虹灯的照明时段和适用地段都是有严格规定的。由此可知，③                  ，光是可以起到美化环境的作用而不是制造光污染的。

阅读短文，判断句子“正确”还是“错误”。

    Lily and Lucy are twins. They come from America. They came to China in 2004 because their parents came to China to work. Their father is an engineer, and their mother is a teacher. Lily and Lucy are 12 years old. They are in Grade 5, but they are in different classes. Lily is in Class 1 and Lucy is in Class 3. They walk to school every day. They have many friends in China. The girls and their friends often play together. They like hiking with their friends in summer and making snowmen with them in winter. They enjoy their life in China.

PM2.5是指大气中直径小于或等于2.5μm（1μm=0.000001m）的颗粒物，也称为可入肺颗粒物，它们含有大量的有毒、有害物质，对人体健康危害很大.2.5μm用科学记数法可表示为____ m．