题干
—________ your son ____ a camera ?
—No, He ___________ one this summer vacation
A：Has; bought ; will buy
B：Did; buy ; bought
C：Does; buy ; bought
D：Does; buy ; will buy
答案(点此获取答案解析）
A
pZ(g)＋qQ(g)，式中m、n、p、q为化学计量数。在0～3 min内，各物质物质的量的变化如下表所示：