In 2019, she was selected by the BBC as one of     1     of science in the 20th century along with Albert Einstein and Alan Mathison Turing. Tu Youyou     2     in being a scientist during a difficult time for science in China, her ability to use old wisdom and new methods to achieve her goals and the fact that her work     3    ,     4    .

Your teeth may be part of your smile,     1    they have a more important job — they are the first step in the process of digestion. You have three     2    (kind) of teeth. In the very front of your mouth are eight flat, thin teeth called incisors. They are used for cutting and biting food. Next to these are pointed teeth called canines,     3     also help you tear food. The remaining teeth are molars. These teeth have flat tops for crushing and grinding the food.