Explanation:

- Laborious: Characterized by hard work or requiring a lot of effort.

- Unsophisticated (Option 1): Lacking refinement or complexity. This doesn't relate to hard work or effort.

- Profane (Option 2): Irreverent or disrespectful, particularly towards sacred things. It doesn’t connect with the effort-related aspect of laborious.

- Assiduous (Option 3): Showing great care and perseverance. This word aligns well with laborious as it also implies diligence and effort.

- Pompous (Option 4): Excessively self-important or arrogant. This does not match the meaning of laborious.

Answer: Assiduous