阅读下面短文,把A—E 五个句子填入文中空缺处,使短文内容究整。
Long ago, as people got older, there was something wrong with their teeth and it would be very painful.___41___ 
Later people learned that cleaning their teeth was important, but they didn't have toothpaste(牙膏) at that time. ___42___
About 100 years ago someone finally created a kind of cream to clean teeth. Not long after that, the toothpaste tube (管子) was invented, so people could press the toothpaste right onto the toothbrush! ___43___ The army gave brushes and toothpaste to all the soldiers, and they learned to brush teeth twice a day. At that time toothpaste tubes were made of metal. ___44___
Today there are plenty of toothpaste choices; lots of colors and tastes to choose from, and some kinds of toothpaste are made just for children. When you're choosing a kind of toothpaste, make sure it has fluoride (氟化物). ___45___When you brush your teeth, you don't need a lot of toothpaste: just press out a bit.
A. They used lemon juice, salt or other things to clean their teeth.
B. Tooth brushing became popular during the World War I.
C. Fluoride makes your teeth strong and healthy.
D. Today they're made of soft plastic and are much easier to use!
E. To avoid toothache, they had their teeth pulled out.
【文章大意】本文主要谈论口腔清洁的由来以及如何选择牙膏。
41.E【解析】句意：为了避免牙痛，他们拔掉了牙齿。
根据下文“Long ago, as people got older, there was something wrong with their teeth and it would be very painful.（很久以前，随着年龄的增长，牙齿出了问题，会非常痛苦。）”可知此句是“为了避免牙痛，他们拔掉了牙齿。”故选E。
42.A【解析】句意：他们用柠檬汁、盐或其他东西来清洁牙齿。
根据上文“Later people learned that cleaning their teeth was important, but they didn't have toothpaste(牙膏) at that time.（后来人们认识到清洁牙齿很重要，但那时他们没有牙膏。）”可知此句是“他们用柠檬汁、盐或其他东西来清洁牙齿。”故选A。
43.B【解析】句意：刷牙在第一次世界大战期间很流行。
根据下文“The army gave brushes and toothpaste to all the soldiers, and they learned to brush teeth twice a day.（军队给所有士兵刷牙和牙膏，他们每天学刷牙两次。）”可知此句是“刷牙在第一次世界大战期间很流行。”故选B。
44.D【解析】句意：如今，它们是用软塑料制成的，使用起来更方便！
根据上文“At that time toothpaste tubes were made of metal.（那时牙膏管是用金属制成的。）”可知此句是“如今，它们是用软塑料制成的，使用起来更方便！”故选D。
45.C【解析】句意：氟化物使你的牙齿强壮健康。
根据上文“When you're choosing a kind of toothpaste, make sure it has fluoride (氟化物).（当你选择一种牙膏时，要确保它含有氟化物。）”可知此句是“氟化物使你的牙齿强壮健康”；故选C。