**Core Concept**
Tinea versicolor is a superficial fungal infection affecting the skin, primarily caused by the overgrowth of a specific type of yeast. This condition is characterized by the appearance of hypopigmented or hyperpigmented patches on the skin, often on the chest, back, or arms.

**Why the Correct Answer is Right**
The correct answer, **Pityrosporum orbiculare**, is the causative agent of Tinea versicolor. Pityrosporum orbiculare, also known as Malassezia furfur, is a type of yeast that is naturally present on the skin surface. However, in individuals with an altered skin pH or an impaired immune system, this yeast can overgrow and cause the characteristic lesions of Tinea versicolor. The pathogenesis of Tinea versicolor involves the production of keratinase and lipase enzymes by the yeast, which lead to the breakdown of the skin's natural barrier and the appearance of the characteristic skin lesions.

**Why Each Wrong Option is Incorrect**
**Option B:** Candida infection is a different type of fungal infection that primarily affects the mucous membranes and moist areas of the body, such as the vagina or oral cavity. Candida is not associated with Tinea versicolor.
**Option C:** Epidermophyton is a genus of fungi that causes skin and nail infections, including Tinea pedis and Tinea cruris. However, it is not the causative agent of Tinea versicolor.
**Option D:** Trichophyton is a genus of fungi that causes various types of fungal infections, including Tinea corporis and Tinea capitis. However, it is not associated with Tinea versicolor.

**Clinical Pearl / High-Yield Fact**
Tinea versicolor is often mistaken for other skin conditions, such as eczema or vitiligo. However, it can be easily diagnosed with a Wood's lamp examination, which reveals a characteristic yellowish fluorescence of the affected skin.

**✓ Correct Answer: A. Pityrosporum orbiculare**