Blue
Ravenous Bugblatter Beast of Traal
If you go 4th why not 5th for the second attack?
My logic is that if I'm taking fighter as a dip to add to a weapon-wielding class, I'm probably planning on hitting 5th in that class. Getting extra attack twice doesn't add anything, so it would be a dead level.
On the other hand, if I do pick up Fighter 5, I'm probably not going 5+ in another weapon class (except maybe rogue), so it's no longer dipping - it's either a full blown "partner" class or it's my primary class.
Though that does suggest another way to phrase it - "check all the classes that are within 3 levels of your highest level class". These show the ones you are staying with. It's just not particularly accurate in the first 7-8 levels and I would say that if you added up all 5e games, more than 50% of all play time has been spend at levels 1-8.