题目

Give water, save lives A bottle of water may not seem like much to you, but thousands of bottles will be of great help for people who live in drought-hit(遭受旱灾) areas in China. Since last autumn, there has been very little rain in Southwest China. Some places, especially in Yunnan . Guangxi, Sichuan, Guizhou, have experienced a serious drought. Crops (庄稼) died, the land cracked, and wells (井) and rivers dried up. More than 20 million people are having difficulty in finding safe drinking water. After learning about the drought, many people around the country helped by giving water,医生使用听诊器给病人诊断病情，其目的是为了 [　　] A．减少声音分散，增大响度 B．改变音色 C．提高音调 D．增大发声体振幅