The incident cemented their relations.

The correct answer is: cemented.

The word “cemented” means to make something stronger or more secure. In the context of the question, the incident made the relationship between the two people stronger.

The other options are incorrect because they do not mean to make something stronger or more secure.

• The word “destroyed” means to ruin or damage something completely.
• The word “wasted” means to use something carelessly or without getting any benefit from it.
• The word “corroded” means to damage something by eating away at it, especially with rust.
• The word “disintegrated” means to break up into small pieces or parts.