The pupils here all kinds of exercises every day in the past few weeks.
A. keptbusydoing
B. keepondoing
C. havekeptbusydoing
D. havebeenkeptbusydoing
网友回答
A. keptbusydoing
B. keepondoing
C. havekeptbusydoing
(答案→)D. havebeenkeptbusydoing
解析：keep sb.busy doings sth.表示使某人忙于，完成时的被动形式应为have been kept busy doing sth.。