The correct option is D Regular pattern
1.Option D, regular pattern is correct, as the word rhythm means regular/periodic patter of movement or sound. E.g. The doctor checked the rhythm of patients heart beat.
2.Flow means continuous movement and does not represent regular pattern.
3.Measure is used assess the value/size of something.
4.Tempo is speed at which a piece of music is played or speed at which an event happens.
Note: Tempo is a good distract in this question as it is related to musical rhythm.