NodeB跟踪外部参考源时，请保证参考源的精度不低于（）ppm。
A、46ppm
B、4.6ppm
C、0.05ppm
D、0.04ppm
参考答案：B
牛胰岛素由A、B两条链组成，其中B链是：（）
A.30肽
B.31肽
C.20肽
D.21肽
Because a degree from a good university is the means to a better job, education is one of the most sophisticated areas in Japanese fife.
A．complex
B．competitive
C．considerate
D．superficial
