单选题
请阅读Passage One，完成第21—25小题。
Passage One
Years ago，I lived in a building in a large city.The buildin9’S next door was only a few feetaway from mine.There was a woman who lived there，whom I had never met，yet I could see her seated by her window each afternoon，sewing or readin9.After several months had gone by，I beganto notice that her window was dirty.Everything was unclear through the dirty window.1 would say tomyself：“l wonder why that wonlan doesn’t wash her window.It really looks terrible.”
One bright morning I decided to clean my flat.including washing the window on the inside.Late in the afternoon when I finished the cleanin9.I sat down by the window with a cup of cof-fee for a rest.What a surprise!Across the way，the woman sitting by her window was clearly visi-ble.Her window was clean!
Then it dawned on me.I had been criticizing(批评)her dirty window，but all the time l waswatching hers through my own dirty window.
That was quite an important lesson for me.How often had I looked at and criticized others through the dirty window of my heart，through my own shortcomings?
Since then，whenever l wanted to judge(评判)someone，I asked myself first，“Am I lookingat him through my own dirty window?”Then I try to clean the window of my Own world SO that I may see the world about me more clearly.
单选题
The writer couldn’t see everything clearly through the window because__________.