**Core Concept**
The child's presentation is suggestive of a viral skin infection characterized by skin lesions with distinctive histopathological features. The vacuolation of keratinocytes in the spinous and granular layers is a hallmark of this condition.

**Why the Correct Answer is Right**
The linear verrucous plaques on the trunk and vacuolation of keratinocytes in the spinous and granular layers are consistent with a diagnosis of molluscum contagiosum. Molluscum contagiosum is a viral infection caused by the molluscum contagiosum virus (MCV), which affects the skin and produces characteristic skin lesions. The virus infects the keratinocytes, causing them to become vacuolated and leading to the formation of characteristic molluscum bodies.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a relevant diagnosis for the child's presentation. The description of linear verrucous plaques and vacuolated keratinocytes does not match the typical presentation of warts, which are usually solitary, verrucous lesions.

**Option B:** This option is not a relevant diagnosis for the child's presentation. The description of linear verrucous plaques and vacuolated keratinocytes does not match the typical presentation of eczema, which is characterized by erythematous, scaly, and itchy plaques.

**Option C:** This option is not a relevant diagnosis for the child's presentation. The description of linear verrucous plaques and vacuolated keratinocytes does not match the typical presentation of psoriasis, which is characterized by erythematous, scaly, and well-demarcated plaques.

**Clinical Pearl / High-Yield Fact**
Molluscum contagiosum is a common viral skin infection in children, and it can be transmitted through direct skin-to-skin contact or by fomites. The characteristic skin lesions can be treated with topical therapies, but the diagnosis is often made based on the histopathological features.

**Correct Answer:** C. Molluscum contagiosum.