题目

Once upon a time, there was a man from the State of Chu who loved his sword very much. One day, he was sitting in a boat preparing    61   (cross) a river, when he accidentally    62   (drop) his sword into the water. The people on board reminded him that he should go into the water to find his beloved sword back. The man felt    63   (anxiety), too.    64   , he turned a deaf ear to that. And instead, he    65   (immediate) took out a knife and made a notch（刻痕） on the side of the boat    66    his dear sword fell. The people wondered why he did 如图，在平行四边形ABCD中，点E、F分别在CD、AB的延长线上，且AE=AD，CF=CB．求证：四边形AFCE是平行四边形．