Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to check your dog's circulation [title] Position your dog to take its pulse. [step] Taking the pulse is a way to measure the heart rate and check circulation. The pulse is measured using the arteries, the blood vessels carrying blood away from the heart.

Ending1: [substeps] Checking the presence of pulses is less likely if its heartbeat is louder than normal. [title] Check your dog's pulse using a device or a pulse monitor. Ending2: If you have a live receiver and you can't take your dog's pulse yourself, call an ambulance. [substeps] The fastest way to tell the difference between an abnormal pulse and a normal pulse is to check blood pressure. Ending3: It is felt when the heart pushes blood through the arteries, causing them to expand. Taking the pulse will be easier when your dog is comfortable and still. Ending4: You can easily look up your dog's pulse by taking a separate inch or a millimeter sized object about the size of a phone card and touching the object so you can feel its pulse. [substeps] Stand just a few feet away from your dog, rather than stationary.

Answer format: ending1/ending2/ending3/ending4