定中心板能点出镜片光学中心、画散光轴向、确定镜片水平和垂直移心量以及确定镜片（）。
A、波纹
B、应力
C、像侧焦点
D、加工中心
参考答案：D
In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet. Spread spectrum simply means that data is sent in small pieces over a number of the (16) frequencies available for use at any time in the specified range. Devices using (17) spread spectrum(DSSS) communicate by (18) each byte of data into several parts and sending them concurrently on different (19) . DSSS uses a lot of the available (20) , about 22 megahertz(MHz).
A．direct-sequence
B．discrete-sequence
C．duplicate-sequence
D．dedicate-sequence
为何每月要对硫化氢检测仪、放射性检测仪进行外观和电量检查？
