secondset reaction

例句：

1. 1. The second set of reactions occurred after the first one.
   第二次反应在第一次反应之后发生。
2. 2. The second set of reactions was slower than the first one.
   第二次反应比第一次反应慢。
3. 3. The second set of reactions involved a different set of chemicals.
   第二次反应涉及不同的化学物质组。