Which one/ones of below may this sentence mean in context?
1) "I chose to study Swedish today rather than going out."
2) "I chose to study Swedish language as my major."
3) "I chose to study Swedish so I constantly practice with the intention of mastering it at the end."
Modals and verbs that behave like modals never take the att. The general rule is that all others do. However, there are quite a few of the latter for which the att is optional, and those you do unfortunately have to learn one by one.