Final answer:
The viral infection that causes rough skin growths known as warts is caused by the human papillomavirus (HPV). Other conditions like oral herpes and chickenpox are caused by different viruses and present differently.
Step-by-step explanation:
Viral Infections Causing Skin Growths
The viral infection that causes rough keratotic skin growths on the top layer of the skin is commonly known as a wart. Warts are caused by the human papillomavirus (HPV). There are other infections that can cause skin issues, like herpes simplex virus (HSV) which usually causes oral herpes and is known for creating lesions on the skin and mucous membranes. However, the rough keratotic growths that the question refers to are not characteristic of HSV but of HPV. Other viruses, such as varicella-zoster virus, can also cause skin conditions like chickenpox and shingles, resulting in rashes and possibly other more serious complications. Yet, these present differently compared to the rough skin growths caused by HPV. Therefore, the correct answer to the question is a. wart.