题目

At celebrations, people should stop ____ fireworks to reduce pollution.A.setting off B.turning off C.taking off D.getting off 答案：【答案】A【解析】句意：在庆祝活动中，人们应该停止燃放烟花爆竹以减少污染。考查动词短语。setting off引爆；turning off关闭；taking off起飞；getting off下车；从文字的表层意思推断空格指停止燃放烟花爆竹，故选A。如图，长方体ABCD-A1B1C1D1中，AB=AD=1，AA1=2，点P为DD1的中点．（1）求证：直线BD1∥平面PAC；（2）求证：平面PAC⊥平面BDD1B1；（3）求CP与平面BDD1B1所成的角大小．