This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
Antigenic shift - 
Select and explain. 
A. Occurs every 2-3 years, B. Gradual change over time, C. Results from genetic recombination, D. Occurs in all influenza viruses
C: Results from genetic recombination
Answer: C: Results from genetic recombination 
Explanation: Antigenic shift is an abrupt, drastic, discontinuous variation in the antigenic structure resulting in a novel virus strain unrelated antigenically to predecessor strain. REF: Anantha Narayan AND PANIKER'S TEXTBOOK OF MICROBIOLOGY 9TH EDITION PAGE NO:499