多选如图所示，波源S1在绳的左端发出频率为f1、振幅为A1=2A的半个波形a，同

根据句意和首字母提示补全单词。

1. You had better brush your t________ twice a day.

2. You can i________  your English if you study hard.

3. The good news s________ very fast. We all know it now.

4. Walking is a good exercise and it is n________ for your health.

5. The classroom is so noisy that we can't hear the teacher c________.

变彩效应是光由于（）或（）所形成的。

在PS版显影机中，保证显影液的均匀性和消耗量的及时补充的装置是：（）。

A.涂胶装置

B.排水装置

C.干燥装置

D.液体循环和补充装置

简述洪水定义。

显示卡PCB的设计要求是在相邻的两条迹线之间，留出足够大的间距。有些迹线必须限制它有最大长度。