题目

圆内接四边形ABCD，∠A，∠B，∠C的度数之比为3∶4∶6，则∠D的度数为( ) A．60°                        B．80°                        C．100°                      D．120° 答案：C 【分析】 根据圆内接四边形的对角互补的性质列式计算即可. 【详解】 解：根据圆内接四边形的性质可得：∠A+∠C=∠B+∠D=180°， 设∠A=3x，则∠B=4x，∠C=6x， 则3x+6x=180°，解得：x=20°， 则∠B=80°，∠D=180°－80°=100°. 故选：C 考点：圆内接四边形的性质.Mary parents buy everything their children want. If they go on(继续) doing so, the children won’t know that money  61  from hard work. When they grow up, they will waste(浪费) money but not  62  it.Some parents like having birthday parties  63  their children. If they go on doing so, the children will think they  64  enjoy birthday parties every year. They may forget their parents’ birthdays and only remember  65 .Many parents don’t let their children do chores. They think children have only one thing  66  . They should study hard  67  be good at their lessons. If parents go on doing so, children will think their parents should do  68  and won’t like cleaning the floor or the desk   69  they find a job. Parents should teach children to do chores because it can make them  70  and help them like work.小题1:A．keepsB．leavesC．comesD．goes小题2:A．saveB．takeC．makeD．cost小题3:A．withB．withoutC．toD．for小题4:A．needB．shouldC．mayD．would小题5:A．theirsB．theyC．themD．themselves小题6:A．doB．to doC．didD．doing小题7:A．butB．alsoC．andD．so小题8:A．choresB．homeworkC．shoppingD．reading小题9:A．afterB．beforeC．untilD．till小题10:A．boredB．nervousC．sadD．healthy