Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to care for baby guinea pigs [title] Measure the size of your guinea pig cage. [step] Pups will reach adult size very quickly, so it is recommended to have your pups in a cage that is an adequate size for an adult guinea pig. The cage should be at least 7.5 square feet.

Ending1: [substeps] Make sure it is easily accessible for your pups, as he/she will experience injury later and will not be able to use the cage for prolonged periods of time. [title] Measure your guinea pig's rear legs. Ending2: This ensures a comfortable temperature during heating and cooling. [substeps] The cage should also be approximately 0.25 inches (1.9 cm) by ½ inch (1.3 cm x 1.5 cm). Ending3: A guinea pig under 12 inches in size should fit 4 litters. Pups 6-12 inches in size would fit 2 litters. Ending4: If you purchased pups from the pet store, make sure that the cage is large enough before you leave the store. [substeps] Even though the cage may seem a bit big for your pups, they will appreciate the extra space they will have to run and explore their environment.

Answer format: ending1/ending2/ending3/ending4