So I was wondering if someone could clear up when you are allowed to omit と when listing things and when it's usually recommended to omit と.
Here are some examples of sentences I found in a book that either omit と altogether or only omit one or two and it's confusing.
On this trip I traveled mainly around southern Europe, to Spain, Italy, and France
Why in the above sentence do they omit と after スペイン and イタリア but include it after フランス?
Then in the following sentence they omit と altogether:
During the summer vacation I traveled around three countries: Thailand, Malaysia, and Indonesia.
Then in the next one they include と between the first and second noun but leave it between the second and third noun:
We have a beginners' class on Mondays, Wednesdays, and Saturdays.
Does this mean that you can choose to use と or leave it out when you like?