题目

阅读下面材料，在空白处填入适当的内容（不多于3个单词）或括号内单词的正确形式。 English is a language (speak) all around the world. There are more than 42 countries the majority (大多数) of the people speak English. Most native speakers of English (find) in the UK, the US, Canada, and many other countries. In total, for more than 375 million people English is their mother tongue. equal number of people learn English as a second language. However, the number of people who learn English as a foreign language (be) more than 750 million. In only fifty ye如图是沿x轴正方向传播的一列简谐横波在某时刻的图象，已知该波的波速为20m/s，则（　　）A、经过0.1s，质点a运动到质点b的位置B、经过0.2s，质点a的速度最小，加速度最大C、经过0.2s，质点a的动能开始减小，势能开始增大D、该波能与一列频率为10Hz的波发生干涉现象