Final answer:
The human immunodeficiency virus (HIV) is more widespread in the human population than the Ebola virus, making it the correct answer to the question.
Step-by-step explanation:
The question 'Which of the following viruses is most widespread in the human population?' is assessing knowledge of viral epidemiology. Among the options provided, 'A. human immunodeficiency virus (HIV)' and 'B. Ebola virus', the human immunodeficiency virus (HIV) is significantly more widespread in the human population.
HIV, the virus that causes AIDS, has been a global pandemic affecting millions of people worldwide. In contrast, the Ebola virus, while highly fatal, has caused sporadic outbreaks with a much more limited geographical spread and a lower total infection count compared to HIV. Therefore, the correct answer is 'A. human immunodeficiency virus.'