闭合的金属环处于随时间均匀变化的匀强磁场中，磁场方向垂直于圆环平面，则(　　)

A．环中产生的感应电动势均匀变化

B．环中产生的感应电流均匀变化

C．环中产生的感应电动势保持不变

D．环上某一小段导体所受的安培力保持不变

J. K Rowling’s career really ________ when Harry Potter and the Philosopher’s Stone was published in June 1997 and achieved instant success.

A．showed off

B．took off

C．paid off

D．put off