NP难问题未必是NP问题
A、正确
B、错误

单项选择题水锤波的周期为（） A. L c B. 2L c C. 3L c D. 4L c

单项选择题Which of the following is an example of externally caused behavior?( ) A.An employee is late because he was partying late and then overslept. B.An employee is late because of a flat tire. C.An employee was fired because he slept on the job. D.An employee was promoted because he was hard working. E.An employee died from lung cancer after excessive tobacco use.