企业员工在劳动安全卫生保护工作中的职业道德行为准则不包括()。
A．安全第一
B．效益第一
C．预防为主
D．以人为本
参考答案：B
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（71） frequencies available for use at any time in the specified range. Devices using（72） spread spectrum (DSSS) communicate by （73） each byte of data into several parts and sending them concurrently on different （74） . DSSS uses a lot of the available （75）, about 22 megahertz (MHz).
72（）
A．direct-sequence
B．discrete-sequence
C．duplicate-sequence
D．dedicate-sequence
静脉肾盂造影检查的禁忌证是（）
A. * * 狭窄
B.腹膜后包块
C.妊娠期及产褥期
D.不明原因的血尿
E.肾性高血压筛选
