Reading
Read the passage then answer the questions
Since many people today like to have clean, bright white teeth, it is surprising that toothbrushes only became common in the twentieth century. But just because people haven’t been using toothbrushes doesn’t mean that they haven’t always tried to keep their teeth clean and their breath fresh. People have cleaned their teeth in a variety of different ways for thousands of years. For example, they used a device called a chewstick. This was a small, thin stick, about the size of a pencil that people chewed on, to remove food and debris from their teeth. Chewsticks were made from special trees that smelled and tasted good so that they would also freshen the mouth and breath. Some form of chewstick was used all over the world for thousands of years. Another way that people cleaned their teeth was by rubbing baking soda or chalk on them. The first bristled toothbrush, or toothbrush with stiff hairs on the end, originated in China almost six thousand years ago. In 1780, the first toothbrush was mass-produced in England by William Addis. These toothbrushes were made of animal bone. The bristles on expensive toothbrushes were badger hair. By the early 1800s, bristled toothbrushes were in general use in Europe and Japan. As technology progressed natural bristles were eventually replaced by synthetic bristles. The first toothbrush with nylon bristles became available in 1938. The first electric toothbrush was invented in Switzerland in 1954. In January 2003, Americans chose the toothbrush as the number one invention that they could not live without.
The toothbrushes only became common in the ________ century