Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to introduce two guinea pigs to each other [title] Determine the sex of your guinea pigs. [step] Sex makes a big deal when it comes to how guinea pigs interact with one another. Before you introduce them, you must determine their sex.

Ending1: [substeps] Male guinea pigs are generally about 4 to 6 months old. Female guinea pigs are about 4 to 6 months old. Ending2: As an example, red or pink guinea pigs each have three characteristics that make them ideal if not vaccinated against the common genital disease. [substeps] Red or pink guinea pigs are naturally " friendly " to other guinea pigs. Ending3: [substeps] The scrotum will be more distinct than the c-section and grow outward, while the c-section will have further internal organs within it. A male or female guinea pig will have slightly larger, fuller genitalia (male) and a wider vulva (female). Ending4: Pet shop employees often make mistakes, and if you're buying a guinea pig from a pet store the chance of error is even higher. [substeps] You should examine your guinea pig on the floor or a very low table.

Answer format: ending1/ending2/ending3/ending4