题目

   Anna lived on the side of a valley(山谷). One summer, there was a very big  36  , and a lot of houses down below Anna’s were washed away. Anna’s house was  37  enough to escape the flood, so when the water had  38  and the other houses were  39  there with no roof and no walls and all covered with mud(泥), her house was just all right.Her house was quite small, her husband was dead, and she had four children, 40 Anna took in one of the families that had lost  41  in the flood and she  42  her home with them until it was  43  for them to rebuild their house.Ann请用所学化学知识解释下列原理。（1）在去除衣服上油污的过程中，洗涤剂起什么作用？_______（2）在铁制品表面涂油、刷漆或镀铬等都能防止铁生锈，其原理是什么？_______