题目

I was shopping in a supermarket last night when I saw a homeless woman with a trolley（手推车） full of all her things. She was sitting inside to keep   41  . I went up to her and tried to give her   42   for something to eat. She wouldn’t   43   it. I said I wanted to help her,   44   she said that if enough money was given to her that day and she had money on her, other homeless people would   45   it from her while she slept. I   46   that I wanted to help her and asked if I could buy her something warm.   47  , she said no. She thanked me and said h如图，在△ABC中，DE∥BC，△ABC的高AM交DE于点N，BC=15，AM=10，DE=MN，求MN的长．