Most important lesson

During my second month of uni, our teacher gave us a pop quiz. I was a conscientious student and had breezed through the questions, until I read the last one: "What is the first name of the woman who cleans the university ?"
Surely this was some kind of joke. I had seen the cleaning woman several times. She was tall, dark-haired and in her 50s, but how would I know her name? I handed in my paper, leaving the last question blank.
Just before class ended, one student asked if the last question would count toward our quiz grade. "Absolutely," said the teacher. "In your careers, you will meet many people. All are significant. They deserve your attention and care, even if all you do is smile and say 'hello'."
I've never forgotten that lesson. I also learned her name was Dorothy.