Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to keep ticks from your dogs [title] Use a tick repellent collar on your dogs. [step] Having your dogs wear a tick repellent collar can help keep ticks away from their heads and necks. These types of collars sit on your dogs' skin and release chemicals or active compounds into the fatty tissue just below your dogs' skin.

Ending1: When you place the collar on your dogs, turn it clockwise until the tick is all the way off your dogs neck. [substeps] Wear the tick repellent collar on all of your dogs throughout the day or whenever you clean your dogs. Ending2: Make sure they wear the collar year round. [title] Purchase pet repellent collars. Ending3: [substeps] Tick repellents can be bought at pet supply stores or online. Follow the directions on the packaging, or ask a salesperson for advice. Ending4: [substeps] These chemicals won't hurt your dogs, but they will kill and repel ticks. Place the collar carefully on your dogs so that they won't be able to turn their heads and chew or bite it.

Answer format: ending1/ending2/ending3/ending4