—What are you going to do this summer vacation?

—Well, you know _______ volunteers will work for the Olympics in Beijing. I want to be one of them. [ ]

A. thousand of

B. thousands of

C. thousands

有等质量的两种金属，前者放入质量分数为10%的稀硫酸中，后者放入质量分数为20%的稀盐酸中，产生氢气的质量随时间变化曲线如图所示。下列说法错误的是

A．产生氢气物质的量相等

B．金属的活泼性A>B

C．酸都反应完了，金属一定都有剩余

D．消耗的稀硫酸和盐酸中溶质的物质的量之比一定是1:2