—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
网友回答
A. worked
B. were working
C. work
(答案→)D. have been working
解析：考查时态。句意：这些科学家发明了一个机器人来照顾孩子。——不奇怪。他们一直在创造奇迹。可知下文描述的是现在已经完成的过去一直在进行的动作，故用过去进行时态。选D。