----- As we know, you won’t go back to the USA since you have established a research center here．But how long _____ in America?

   ----- For almost 10 years．

       A．did you study                       B．have you studied 

       C．were you studying                   D．have you been studying

—As we know, you won’t go back to the USA since you have established a research center here．But how long _____ in America?

   —For almost 10 years．

       A．did you study                       B．have you studied 

       C．were you studying                   D．have you been studying

----- As we know, you won’t go back to the USA since you have established a research center here．But how long _____ in America?
----- For almost 10 years．

（2010·黑龙江省哈九中高三三模）26．----- As we know, you won’t go back to the USA since you have established a research center here．But how long _____ in America?

   ----- For almost 10 years．

A．did you study                 B．have you studied 

       C．were you studying             D．have you been studying

（2010·黑龙江省哈九中高三三模）    26．----- As we know, you won’t go back to the USA since you have established a research center here．But how long _____ in America?

   ----- For almost 10 years．

A．did you study                 B．have you studied 

       C．were you studying             D．have you been studying