**Core Concept**
HIV (Human Immunodeficiency Virus) infection is a significant public health concern worldwide. The virus primarily targets and infects CD4+ T lymphocytes, also known as T helper cells, which play a crucial role in the immune system. Individuals with compromised immune systems or those engaging in high-risk behaviors are more susceptible to HIV infection.

**Why the Correct Answer is Right**
HIV infection can be transmitted through various routes, including sexual contact, blood transfusions, and sharing needles. Individuals who engage in unprotected sex, have multiple sex partners, or use intravenous drugs are at an increased risk of acquiring HIV. Furthermore, individuals with certain medical conditions, such as genital ulcers or mucosal trauma, may also be more susceptible to HIV transmission due to increased viral entry into the body.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a high-risk group for HIV infection. While older adults may be more susceptible to HIV due to age-related immune decline, this option is too vague and does not accurately convey increased risk.

**Option B:** This option is incorrect because individuals with a history of syphilis are not inherently at increased risk for HIV infection. However, they may be more likely to engage in high-risk behaviors, such as unprotected sex, which increases their risk of HIV transmission.

**Option C:** This option is incorrect because individuals with a history of tuberculosis (TB) are not at increased risk for HIV infection. However, people living with HIV/AIDS are more susceptible to TB due to compromised immune function.

**Clinical Pearl / High-Yield Fact**
It is essential to note that HIV can be transmitted through perinatal exposure, healthcare-associated transmission, and occupational exposure. Healthcare workers should exercise caution when handling blood and bodily fluids to prevent HIV transmission.

**Correct Answer:** C. Individuals with a history of genital ulcers or mucosal trauma may be at increased risk for HIV infection due to increased viral entry into the body.