【2014·全国卷Ⅰ】阅读下面短文，从短文后各题所给的四个选项（A, B, C, D）中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
As a general rule, all forms of activity lead to boredom when they are performed on a routine basis. As a matter of fact, we can see this ____41____at work in people of all _____42____. For example, on Christmas morning, children are excited about ___43____with their new toys.
