— It is said that Jack is very rich and is always changing his private cars. What is he?

— ________, I am not sure. [ ]

A. Somebody of a manager

B. Something of a manager

C. Anyone of a manager

D. Anything of a manager

真空中的一切电磁波都具有相同的（　　）

A．波长

B．能量

C．频率

D．波速