Multiple choice Contractions of the external intercostal muscles bring about decrease in the volume of thoracic cavity increase in the volume of thoracic cavity flattening of the diaphragm no change in the <font size="2">v</font>olume of thoracic cavity Reveal answer Fill a bubble to check yourself B Correct answer Explanation Contractions of the external intercostal muscles bring about increase in the volume of thoracic cavity.