题目

 We all face quantities of stresses in day-to-day living, whether at work, in the home, or anywhere in between．   36    Here's how stress can help us on an everyday basis．     ◆Sharpe rung your memory．     Did you ever notice that sometimes when you are stressed, your memory seems to improve? Remember that test you passed where the answers seemed to come out of nowhere?    37  It's because of stress hormones（荷尔蒙）that increase your alertness when it's most needed．     ◆    38     Successful employees turn stress into motivation．Have you 室内污染的主要成分之一——甲醛(化学式为CH2O)，它来源于室内装潢所用的油漆胶合板等材料。下列关于甲醛的说法正确的是（     ） A．甲醛是一种氧化物          B．甲醛中碳元素质量分数为40% C．甲醛分子中含有氢分子 D．甲醛是由一个碳原子和两个氢原子、一个氧原子构成