**Core Concept**
The diagnosis of a painless indurated ulcer with everted margins on the penis is suggestive of primary syphilis, specifically chancre. This condition is caused by the bacterium *Treponema pallidum*, which is transmitted through sexual contact.

**Why the Correct Answer is Right**
The presence of a painless, indurated ulcer with everted margins is a classic clinical presentation of primary syphilis. The chancre typically appears 3-4 weeks after exposure to the bacterium and resolves spontaneously within 2-6 weeks. The infection can be diagnosed through serological tests, such as the rapid plasma reagin (RPR) or Venereal Disease Research Laboratory (VDRL) tests, which detect the presence of antibodies against *Treponema pallidum*.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** This option is not provided. However, other conditions like herpes simplex or lymphogranuloma venereum can cause ulcers on the penis but typically present with painful lesions and systemic symptoms.
* **Option C:** This option is not provided. However, other sexually transmitted infections like chancroid or donovanosis can cause ulcers on the penis but are less likely to present with the characteristic painless, indurated chancre of primary syphilis.
* **Option D:** This option is not provided. However, other conditions like balanitis or dermatitis can cause lesions on the penis but are not typically associated with systemic symptoms or serological tests for syphilis.

**Clinical Pearl / High-Yield Fact**
The "rule of nine" in syphilis states that the chancre typically resolves within 9 weeks, and the patient becomes seropositive within 9 months. This rule can be a helpful mnemonic for remembering the typical timeline of primary syphilis.

**Correct Answer:** C. Chancre