问题
选择题
—Those scientists invented a robot to care for kids!
—It's not surprising. They ________ wonders all the time.[ ]
A. worked
B. were working
C. work
D. have been working
答案
答案：D
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—Those scientists invented a robot to care for kids!
—It's not surprising. They ________ wonders all the time.[ ]
A. worked
B. were working
C. work
D. have been working
答案：D