—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. has been working C. worked D. had worked
—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. has been working C. worked D. had worked
C