Could you tell me on what day________the Palace Museum for free？
A.can elementary and high school students visit
B.could elementary and high sehool students visit
C.elementary and high school students can visit
D.elementary and high school students could visit
网友回答
C解析分析：不要把主句的could看成是过去时，这里是“请求对方做事情”的句型，表示“客气”。A、B项词序错误。按句意是“免费参观”，这里指经常性的事情。