Please choose the correct ending to complete the given sentence: Health: [header] How to recognize syphilis symptoms [title] Understand how people get syphilis. [step] Once you understand how people pass syphilis to one another, you can figure out whether you're at risk. The disease is transferred from one person to another through contact with a syphilis sore.

Ending1: These sores may appear externally on the penis and outer vaginal area, or internally in the vaginal canal, anus, and rectum. They may also be present on the lips and inside the mouth. Ending2: This contact is painless and often causes no injury to either the person or yourself. [substeps] The sores are very slow to heal and you may experience painful reactions. Ending3: If you get infected, you're at much higher risk for developing syphilis. Syphilis sores are a black, painful blister that develops on the affected skin over time. Ending4: One reason people get syphilis is because they become pregnant or have children. It is not always clear if one person is at risk because their immune system crashes.

Answer format: ending1/ending2/ending3/ending4