题型：填空题 He was thinking about the problem when an apple fell off the tree, _____ him right on the head.[ ]A. hit B. having hit C. hitting D. and hitting 查看答案
题型：填空题 已知下列四个命题：①平行于同一直线的两平面互相平行；②平行于同一平面的两平面互相平行；③垂直于同一直线的两平面互相平行；④与同一直线成等角的两条直线互相平行．其中正确命题是（ ）A．①②B．②③C．③④D．②③④ 查看答案