Final answer:
The most helpful preventive measure for a client with asthma sensitive to house dust-mites is to use air filters in the furnace system.
Step-by-step explanation:
The most helpful information to provide to the client with asthma who is sensitive to house dust-mites would be to use air filters in the furnace system.
Air filters in the furnace system can help to remove dust mites and other allergens from the air, reducing the risk of asthma episodes. Changing pillow covers every month, washing bed linens in warm water with a cold rinse, and washing and rinsing bed linens in hot water may also be beneficial, but using air filters in the furnace system would be the most helpful preventive measure.