题目

完形填空 She wasn't aiming to make history. But in the late 1990s, when Sumita Mitra, a chemist at 3M, 1 to use nanotechnology(纳米技术) to improve dental (牙齿的) fillings, that's exactly what happened. Now 2in dental offices— and almost every mouth, her fillings are certainly one of the life-changing 3. Any invention starts with a 4 and so did Mitra's fillings. Before themid-1990s, fillings came in two different 5. One wasn't strong enough forstress-bearing 6 of the teeth like biting surfaces, and theother was strong but could become rough from 7 and chewing. Dentists often had 下列图示的实验操作错误的是（ ）A．滴加液体B．取用固体药品C．倾倒液体D．读取液体体积