Final answer:
The blow-dryer attachment that softens the airflow is the diffuser. It disperses air over a larger area and is ideal for reducing frizz and defining curls or waves.
Step-by-step explanation:
The blow-dryer attachment that causes the air to flow more softly is the diffuser. Unlike other attachments, the diffuser is designed to disperse the airflow over a larger area without blowing your hair around too much. This helps to reduce frizz and style curls or waves more effectively.
The concentrator nozzle focuses the airflow for more precise styling, while a comb attachment helps to straighten the hair as you dry. The straightening attachment usually comes as a brush or comb structure that aids in pulling the hair straight while it dries.