Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to tell when gerbils are mating [title] Listen for thumping sounds. [step] You may also observe the gerbil pounding both rear feet. The sound is usually a quick thump, but can vary in tempo and volume.

Ending1: Yelling at your gerbil will encourage it to mating. [substeps] You may see them making loud thrashing noises, like rocks hitting the ground. Ending2: There are more air conditioners nearby to filter out tumors. Recognize long-lidded gerbils once a day, not hourly. Ending3: This can be mistaken for the gerbil being excited for reasons other than mating. [substeps] Sometimes gerbils other than the mating pair will " catch on " and start pounding their feet too. Ending4: This is because a young gerbil is not aware that their owner and puppy are present. [title] Pay attention to the pink goose's frequent honk.

Answer format: ending1/ending2/ending3/ending4