某标准件图号11290-06251，其中06代表（）
A、该螺栓性能等级
B、该螺栓螺纹公称直径
C、该螺栓螺纹长度
D、该螺栓生产年份
参考答案：B
根据句意及首字母提示，写出单词。
1. We are going to s our homework to our teachers by email in the future.
2. Daming is writing on the b with chalk.
3. They will send their homework to the teachers by e .
4. Everyone will study at home in the f .
5. Mr. Li is t to some parents in the classroom.
有机玻璃纵波波长为1.37mm，其频率为（）。
A、2MHz
B、3MHz
C、2.5MHz
D、1.5MHz
