serial bit

例句：

1. 1. The serial numbers of the cars are all different.
   这些汽车的序列号都不同。
2. 2.She has a series of plans to improve her work efficiency.
   她有一系列计划来提高她的工作效率。
3. 3. This is a serial of books that I have been reading.
   这是一系列我一直在读的书。