**Core Concept**
Dermatophytes are a group of fungi that cause skin, nail, and hair infections in humans. They obtain their nutrients by breaking down keratin, a protein found in skin, hair, and nails. Trichophyton is a genus of dermatophytes that is known to infect hair, nails, and skin.

**Why the Correct Answer is Right**
Trichophyton species, such as Trichophyton rubrum and Trichophyton mentagrophytes, are opportunistic pathogens that cause a wide range of superficial fungal infections. They infect hair, nails, and skin by producing enzymes that break down keratin, allowing them to obtain nutrients. The mechanism of infection involves the production of spores that germinate on the host's skin, leading to the formation of microcolonies and eventually, the development of clinical lesions.

**Why Each Wrong Option is Incorrect**
**Option B:** Epidermophyton is a genus of dermatophytes that primarily affects skin and nails, but it does not typically infect hair. It is the causative agent of athlete's foot and jock itch.
**Option C:** Microsporum is a genus of dermatophytes that primarily affects hair and skin, but it does not typically infect nails. It is the causative agent of ringworm of the scalp and body.
**Option D:** Malassezia is a genus of yeasts that are normally present on the skin and are involved in seborrheic dermatitis, but it is not a dermatophyte and does not infect hair, nails, or skin in the same way as Trichophyton.

**Clinical Pearl / High-Yield Fact**
It's essential to note that Trichophyton species can be transmitted through direct contact with an infected person or animal, as well as through contaminated fomites. This highlights the importance of practicing good hygiene and avoiding close contact with individuals who have active dermatophyte infections.

**✓ Correct Answer: A. Trichophyton**