Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to treat canine tick problems [title] Apply spot-on products. [step] You can apply spot-on tick products directly to your pet's skin. Part their fur and dot on the spot-on product in small amounts.

Ending1: [substeps] Note that these products are available over-the-counter at most pharmacy and pet stores, but you can also buy them online. Some click directly into the skin at the stalk and give an unpleasant unpleasant taste. Ending2: [substeps] Be sure to wash your hands before applying the product. Always wash your hands before eating or drinking with a tick as a dog's saliva can interfere with the application process. Ending3: This should be one application per day, as it needs to build up quickly. [substeps] If you notice problems with the subcutaneous area of your pet's skin, apply a patch of the product to the area. Ending4: Most spot-on products will need to be applied once a month. [substeps] Look for spot-on products that contain pyrethrin, permethrin, fipronil, or imidacloprid.

Answer format: ending1/ending2/ending3/ending4