题目

Can dogs and cats live in perfect harmony in the same home? People who are thinking about adopting a dog as a friend for their cats are worried that they will fight. A recent research has found a new recipe of success. According to the study, if the cat is adopted before the dog, and if they are introduced when still young (less than 6 months for cats, a year for dogs), it is highly probable that the two pets will get along swimmingly. Two-thirds of the homes interviewed reported a positive relationship between their cat and dog.      However, it wasn't all sweetness and light. The下列化学用语正确的是（　　）A．氯化氢的电子式：B．镁的原子结构示意图：C．乙烯的结构简式：CH2CH2D．碳酸钠的电离方程式：Na2CO3?Na++CO32一