Option B (Cow) is the correct answer. The context mentions vaccinia virus and identifies Jenner as the inventor of vaccination in Question 26. The term 'vaccinia' is derived from 'vacca' meaning cow, and historically, the first vaccine was developed by Edward Jenner using cowpox material from cows to provide protection against smallpox. This question tests the fundamental knowledge about the origin of vaccination technology, which is a key concept in the NCERT Biotechnology curriculum.