Inthepast50years,there_____agreatincreaseintheamountofresearch_____onthehumanbrain.
A.was...did B.has been...to be done C.was...doing D.has been...done正确答案D
Inthepast50years,there_____agreatincreaseintheamountofresearch_____onthehumanbrain.
A.was...did B.has been...to be done C.was...doing D.has been...done正确答案D