----Can you guess _________the iPhone4s yesterday?

---- Sorry, I’ve no idea about it.

A．how much did he spend on

B．how could he get

C．where did he get

D．how much he paid for

何谓陀螺仪的定轴性（）。

A．其主轴指向地球上某一点的初始方位不变

B．其主轴动量矩矢端趋向外力矩矢端

C．其主轴指向空间的初始方向不变

D．相对于陀螺仪基座主轴指向不变