Select the INCORRECTLY spelt word.

Solusion

The incorrectly spelled word is "Solusion" 

Explanation of all options:

1. Trustworthy: Correctly spelled. It describes someone or something that is reliable, dependable, and deserving of trust.

2. Bonafide: Correctly spelled. It means genuine, authentic, or in accordance with the law.

3. Solusion: Incorrectly spelled. The correct spelling is "Solution." It refers to an answer, resolution, or remedy to a problem or situation.

4. Cultural: Correctly spelled. It relates to matters pertaining to culture, such as traditions, customs, arts, and beliefs.