,1 ---- Look! Everything here is under construction. ---- Oh, has the building once ___ for exhibition been pulled down, too? A. having been built B. being built C. to be built D. built2. ---- Tom came to work last Sunday, but no one has seen him since. ---- _____ he have had an accident? A. Must B. Should C. Might D. Could问一下老师选什么？为什么？谢谢！

1.这里涉及现在分词，过去分词，分词时态，动词不定式被动，现在完成时变动及非谓动词做定语的区别，不是几句讲的讲的清楚2.涉及时态及虚拟语气学习应扎实基础，举一反万，万不可头痛医头脚痛医脚请加入课堂，课对这样的题有一劳永逸的解决方法