1 I don`t know if they ___ A party next sunday A will have B

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1 I don`t know if they ___ A party next sunday A will have B would have C had D can have 为什么是B 2 2009•兰州）如图,某公路隧道横截面为抛物线,其最大高度为6米,底部宽度OM为12米．现以O点为原点,OM所在直线为x轴建立直角坐标系．
（1）直接写出点M及抛物线顶点P的坐标；
（2）求这条抛物线的解析式；
（3）若要搭建一个矩形“支撑架”AD-DC-CB,使C、D点在抛物线上,A、B点在地面OM上,则这个“支撑架”总长的最大值是多少?为什么oa =bm!谢谢了30分虽然不多

1、if后面接的将来时的虚拟语气啦,自己去看看笔记吧
2、（1）M（12,0）；P（6,6）
（2）设抛物线方程为y=a(x-x0)^2+b然后将M点和P点的坐标带进去就能求出来了,答案省略
（3）oa=bm这是显然的啦,因为是对称的啦,而且求的是最大值啦.
【亲,还是好好学习吧!既然是简单的题目,那我相信你也是可以做出来的.】
再问：还不不知道为什么oa=bm 知道P是对称轴上的点或者说对称怎么知道OA =bm的

I don‘t know if they ——(have)a party next week. will they have a party?I don't know.(合并未含有if引导的宾语从句的复合句) I don't know ____ they have passed the exam.A.what B.if C.wh 一道英语题：I don't know if we ___(hold) a sports meeting next mon I don't know when ___(have) a farewell party for them I don't know when they are going to have a welcome party. I will go to Korea next month .Why ___ me?A.don't join B.don they will have a god time at the party next sunday同义句英语连词成句 :1.have.will.they.next.party.Sunday.a.afternoon i don't know if we will have a colorful and a happy life. we will have a party( )seven( )next Sunday 连词成句:will party Sunday we a have next(.)