题目

    Having finished her homework, Ma Li wants some music for relaxation. As usual, she starts her computer and goes to Baidu.com to download music files. But this time she is surprised when an announcement about protecting songs’ copyright bursts onto the screen. The age of free music and movie downloads may have come to an end as Web companies like Baidu are accused of pirating copyright. Lawsuits (诉讼) have been filed against four websites offering free downloads. In September 2005, a Beijing court ordered Baidu to pay recording company Shanghai Push compensation for their losses. Ba15．某反应前后分子变化的微观示意图如下，下列说法正确的是（　　）A．反应物与生成物共有3种物质B．反应后原子个数增多C．该图可示意CO与O2的反应D．反应物中元素的化合价都为0