阅读下面材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。
When I was in elementary school, I always argued with a boy in my class. I have forgotten what the ______ (argue) was about, but I have never forgotten the lesson I learnt that day.
I was convinced that “I” was right and “he” was wrong but he argued that “I” was wrong and “he” was right. The teacher decided to teach us ____ very important lesson. She____ (bring) us up to the front of the class and placed the boy on the side of her desk and me on the other. In the middle of her desk, there was a large ______ round object. She asked the boy what color the object was. “White”, he answered. I couldn’t believe ______he said, because it was _____(obvious) black! Another conflict started ____ him and me, but this time it was about color of the object. The teacher told me to stand in the place _____the boy had been standing. We changed the place and now she asked me what the color of the object was. I had to answer, “White”. It was an object with two differently colored sides. From ____viewpoint it was white, but from my side it was black. Sometimes____ (look) at a problem from the other person’s view, we will come to a totally different conclusion.