Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to treat head tilt in gerbils [title] See if your gerbil is having difficulty walking straight. [step] Gerbils with head tilt will often walk or run in a continuous circle. With the imbalance that causes a head tilt, your gerbil won't be able to walk or run in a straight line.

Ending1: [substeps] If you notice your gerbil moving this way, keep an eye on it until you can get it to the vet. Walking in a tilt won't hurt your gerbil, but running into walls or furniture because it's off balance will. Ending2: However, they will be able to keep up with their surroundings without this imbalance. [substeps] To accommodate head tilt, give your gerbil constant instructions when you notice their head tilting 90 degrees. Ending3: They'll also lose whole heads through suddenly shrinking pieces of fat or tissue. [substeps] If your gerbil struggles to walk straight, their heads may be enlarged due to head tilt. Ending4: The addition of this imbalance to the upper or lower part of the body forces the head tilt against the spinal column. Change your gerbil's position so that he or she is standing upright.

Answer format: ending1/ending2/ending3/ending4