—Isn’t it a great surprise that I happened to meet my university English teacher at the South Bank Parkland last week?
—How long ____ you _____ each other, then?
—This returned scholar has become one of the top experts in this field.
—Yes, I know him very well. He ______ for ten years at an institute in the USA.
A. has worked B. had worked C. worked D. has been working