题目

During the time of the Second World War, a woman from New York was one of the many who had a son in the army in __41__. The son __42__ home once a week. His mother was always __43__ to receive his letters, so when the letters __44__ stopped coming, she became worried. She soon __45__ from the Home Office that her son was __46__ by the Japanese. And he was now in__47__. A few weeks later, the mother was __ 48__ happy to get a letter from her son. He wrote that he was in a Japanese prisoner of war camp, __49__ he was treated well and was in __50__ health. At the end of the letter, he __5在蒸发皿中加热蒸干并灼烧（低于400℃）下列物质的溶液，可以得到该物质的固体的是（     ） A．AlCl3          B．NaHCO3        C．MgSO4        D．KMnO4