题目

阅读下面材料，根据其内容和所给段落开头语续写两段，使之构成一篇完整的短文。I'djust returned from a beautiful fall early-morning walk with my dog. At thefront door, I dug around in my pockets for the keys. When I discovered I didn'thave them, I decided to return to the paths we'd taken. I would surely spotthem in plain sight. My little dog ran in circles of excitement that we woulddo a repeat of our just-finished outing. I spent an hour looking, brushing asidetall grasses, but the keys remained lost. I was beginning to get upset as Ithought of the results of 设m，n是两条不同的直线，α，β是两个不同的平面，下列命题中正确的是(    )A．若α⊥β，m?α，n?β，则m⊥nB．若α∥β，m?α，n?β，则m∥nC．若m⊥n，m?α，n?β，则α⊥βD．若m⊥α，m∥n，n∥β，则α⊥β