题目

When my son, Mark, was in the third grade, he saved all his pocket money for over three months to buy holiday presents for those he loved. The third Saturday in December Mark said that he had made his list and had twenty dollars in his pocket. I drove him to a nearby supermarket. Mark picked up a hand basket and went off on his own while I waited patiently reading a book in the car. It took Mark over 45 minutes to choose his presents. The clerk rang in his purchases(所购物品) as I politely looked the other way. Mark kept within his budget(预算) and reached into his pocket for his劣质的油性油漆、板材、涂料、胶粘剂等材料含有较多的甲醛、苯、二甲苯等有毒有机物，用来装修房屋，会造成室内环境污染，这是因为有毒有机物分子都在做永不停息的无规则运动，这种现象在夏天时特别严重，因为_____越高，_____越剧烈。