Explanation:

- Repercussion: This word is spelled correctly. It means an unintended consequence of an event or action, especially an unwelcome one.

- Obsolescing: This is correctly spelled. It describes the process of becoming obsolete or outdated and no longer used.

- Sillhoutte: This word is not spelled correctly. The correct spelling is "silhouette," which refers to the dark shape and outline of someone or something visible against a lighter background.

- Ludicrous: This word is correct. It describes something so foolish, unreasonable, or out of place as to be amusing.

Option:3 - Sillhoutte is incorrectly spelt. Capitalize Option 3