Help for selection rules

[KFC]

I am reading some online article on Zeeman effect
http://math.ucr.edu/home/baez/spin/node10.html
In the article, the author mentions 4 selection rules, I wonder the corresponding transition is allowed by satisfying one of these selection rules or the corresponding line will be allowed only when all rules are satisfied?

Thanks.

[clem]

All four selection rules must be satisfied.