阅读下面材料，在空白处填入一个适当的词（1个单词）或括号内单词的正确形式。
My father ____( work) in an office. There ____ two large windows in it. One day, a woman in a ____(pass) car looks up and sees my father. My father waves his hands, ____ the woman waves back. This gives my father an idea.
Later, he changes his way of ____ ( greet) people. He writes signs, like “Hello” ____ “Be happy”. Every afternoon when people go home from work, my father will greet them with the signs. Then they will give my father big smiles.
The day when I come into the world, my father puts a sign ____ the window, “I’m a new father!” To his ____ (surprise), some of people hold a sign saying, “Congratulations!”
My father learns the ____ ( true) in the saying, “You smile, and the whole world smiles with you.” And he becomes ____ first one who greets strangers with signs every day.
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