题目

    Bobby Qualls was shopping when he received a text message: Fire on Beechmont, one-story house, child trapped inside. “I was picking out gifts for the family our engine house adopted for Christmas,” remembers Qualls, who has been fighting fires in Memphis for 24 years. “I had this sinking feeling as I got in my car and headed over.”     The last time Qualls had been on Beechmont Street was to install smoke detectors (感应器) at the Bateman-Tubbs home. He’d been on a secret task to see if they needed extra help during the holidays. There he discovered that the four 如图表示在一定条件下发生的某化学反应，则下列说法中正确的是（ ）A．该反应属于化合反应B．反应后分子个数不变C．反应后原子个数变少了D．两种反应物均为化合物