请问一串名词时，过程中的逗点，何时才要加/不加/可加可不加?
具体的情况:
1. A and B 或者 A or B 这不加逗点
2. A, B and C 或者 A, B or C 不加逗点
还是说也可以加逗点如下?
A, B, and C 或者 A, B, or C
但如果更多名词连接一起呢? 逗点何时必加
，何时必不加而何时可加可不加呢?
例如以下从书中摘录的:
1. ... for the purpose of providing medical, surgical, hospital
care, sickness, accident, disability, death, unemployment or
vacation benefits, apprenticeship or other training programs,
day care centers, scholarship funds, prepaid legal services
or severance benefits
2. First, a "savings clause" allows that state laws pertaining to
the "regulation" of insurance, banking, securities, and generally
applicable criminal laws are not preempted.