— Has Linda come back from Canada?

— Yes. She _____ there for eight years.

A. has stayed    

B. stays    

C. stayed    

D. had stayed

在负载为感性时，三相机电式（感应系）无功电能表的转盘正转;容性时，反转。所以一般机电式（感应系）无功电能表都加装止逆装置或用双向计度器。