三鹿奶粉因掺有三聚氰胺（化学式为C3H6N6），使全国众多婴儿出现泌尿系统疾病，发生了震惊全国的重大食品安全事故．下列有关叙述错误的是（ ）
A．三聚氰胺属于有机物
B．三聚氰胺是一种食品添加剂
C．三聚氰胺分子中原子个数比为C：H：N=1：2：2
D．三聚氰胺中C元素的化合价若为+4价，则N元素的化合价为-3价
A、根据化合物中有无碳元素进行区分，一氧化碳、二氧化碳、碳酸钙等除外，根据化学式可以看出含有碳元素，故A正确，
B、三聚氰胺会使全国众多婴儿出现泌尿系统疾病，故B错误，
C、化合物中原子个数比等于化学式中元素符号的角标的比值，故C正确，
D、碳元素的化合价是+4价，设氮元素的化合价是x，所以 （+4）×3+（+1）×6+6x=0，则 x=-3
故选B．
阅读下面短文,选择恰当的单词填空. 每词限用一次, 其中有两项多余.
Linda and Betty were both nineteen years old. In June, after a school year was over, they decided to take a vacation _小题1:___. They went to several towns and villages, visited some places of interest, saw and heard a lot of interesting things. They _小题2:___ very much. One afternoon, they were going to stay overnight in a small town. It was too __小题3:__ to go further and they wished they could find a river and swim in the cool water. They were driving the car __小题4:__ while they were looking around. Suddenly Linda saw a lake not far away. They drove there fast and _小题5:____ by the lake. They looked around and found a woman sitting on a stone and fishing there. After they ___小题6:_____ and were going to jump into the water, the woman came up to them and shouted, “Sorry, madams. Swimming __小题7:___ in the lake!” “Why didn’t you tell us about it _小题8:______ we took off our clothes?” Betty said angrily. “But it isn’t forbidden to take off clothes by the lake,” said the woman. |