Lecture 15 (Computation Theory) Decidable and Undecidable Languages

In the lecture's hierarchy of languages, which inclusion chain is correct?

1. A.regular ⊆ context-free ⊆ decidable ⊆ recognizable
2. B.regular ⊆ decidable ⊆ context-free ⊆ recognizable
3. C.recognizable ⊆ decidable ⊆ context-free ⊆ regular
4. D.context-free ⊆ regular ⊆ recognizable ⊆ decidable