–He seems to be a student. --No, he __________. A. used to B. used to be C. used to have D. was used to 答案:B完成推理填空:如图所示,已知AD=BC,AB=DC,试判断∠A与∠ABC的关系.下面是小颖同学的推导过程:解:连接BD.在△ABD与△CDB中∵AD=CB (已知)AB=CD (已知)BD=DB (________)∴△ABD≌△CDB (________)∴∠1=∠2 (________)∴AD∥BC (________)∴∠A+∠ABC=180°(________)