问题
选择题
For more than a decade, experts from across the globe ________ on the cure of the disease that way.
A．worked
B．are working
C．have been working
D．were working
答案
答案：C
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For more than a decade, experts from across the globe ________ on the cure of the disease that way.
A．worked
B．are working
C．have been working
D．were working
答案：C