题目

Try, Try Again    There was a king whose name was Tamerlane．He wanted to become the king of the whole world．So he started wars against other countries．He got many cities, but at last his army was beaten．Tamerlane left his own country．    For a long time he moved from place to place．His enemies（敌人）were looking for him．He was about to lose all hope．    One day he was lying under a tree, thinking about his life．Suddenly he saw a small thing climbing up the tree．He looked more closely and saw that it was an ant．The ant was carrying a grain（一粒）of wheat as在一定条件下，某固态化合物X受热分解的反应为：X  △  . A↑+B↑+2C↑，测得反应后生成的混合气体的密度是同温同压下H2密度的12倍，则X的摩尔质量是（　　） A、24g/molB、50g/molC、80g/molD、96g/mol