目前，铅污染已成为威胁我国儿童健康的“隐形杀手”．调查发现，我国儿童血铅水平较发达国家儿童高，血铅增高对儿童神经系统发育、智力发展等方面存在负面影响．威胁儿童的铅污染有四大来源：①汽车尾气污染；②家居装饰用品污染；③玩具和学习用品污染；④食品污染，如爆米花、松花蛋等都含有铅．

血铅含量对人究竟有什么影响呢？有人做了这样一组实验，将质量2.0﹣2.5千克的2只家兔分为两组：

A组：用含1.83%醋酸铅的5%葡萄糖溶液，每3天皮下注射1次，10mg/kg剂量，每隔10天测一次血红蛋白；

B组：用含3.66%醋酸铅的5%葡萄糖溶液，每3天皮下注射1次，10mg/kg剂量，每隔10天测一次血红蛋白．

实验结果如表：

人们的生活已经离不开现代通信，现代通信可分为微波通信、____ 、____ 和____ ．

    December 16, 2013 was my birthday. It was the day ____ my best friend left me. I remember it as if it were yesterday. It was also our Christmas concert. ____(offer) a job in Colorado, my friend's father had to leave our city. And his family had to go with ____(he). Mr. Escalante, our old headmaster, brought her whole family up on the stage, and they made a big ____(announce) about how they ____(leave). After the concert ended, I was in a total mess. I felt as if I had made something torn out of my body that could never be ____(full) replaced. My best friend's name was Hannah Zona.

    Ever since I was a little girl, my family was always with the Zonas. We would go to the fair, did anything you could think of. ____(live) so close ____ each other, we could always go to each other's houses after school. ____she is about 7 years older than me, we act like we are sisters. ____(word) can't describe how much I miss her. When she comes back to California, it's like we were never apart. Hannah Zona is the best friend you could ask for. No one could ever replace her and the love I have for her.