Mary told me that she had been to China ( ) .(two)教教我

问题描述:

Mary told me that she had been to China ( ) .(two)
教教我

这句话的中文意思是“玛丽告诉我她不曾去过中国”
“Mary told me”,即“玛丽告诉我”,已经用了过去式,
分句“she had been to China ”,她没有去过中国是“告诉”这个过去动作的过去,即过去的过去,所以用了过去完成时态.