This letter became the clue to the incident.

His way of speaking is monotone, and it's boring to listen to.

His job is monotonous, repeating the same thing every day.

He bought a new motorcycle.

This problem is simple, so it can be solved quickly.

This soup has a light flavor and is very delicious.

His frankness sometimes surprises people.

He was indifferent to my story.

His room is designed in monochrome.

Protein is necessary for muscle growth.