题目

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。 There is an English saying that goes, “he who laughs last, laughs the hardest.” High School Musical star Zac Efron is laughing a lot these days. , because he was always the smallest in his class and was laughed at because he had a big space between his teeth. In sixth grade, Efron’s basketball team made it to the league championships. In double overtime(两个加时赛)， with three seconds left, he rebounded the ball and passed it----to the wrong team!Now at 21, E可逆反应A(g)+2B(g)  2C(g)(正反应为放热反应)在一定条件下达到平衡，若改变条件，将变化结果(填增大、减小、不变)，填入空格。 （1）升高温度，B的转化率              ，v正             。 （2）保持温度和压强不变，加入稀有气体，则C的物质的量             。 （3）保持温度和体积不变，再加入稀有气体，A的转化率              。 （4）若温度和体积不变，反应从A、B开始至平衡，在这个变化过程中，容器内气体的密度          ，平均相对分子质量           。