Final answer:
The correct word to complete the sentence is 'advises'. The doctor recommends, or advises, a flu shot as a preventative measure, though it does not guarantee complete immunity against the flu.
Step-by-step explanation:
The correct option to fill in the blank in the sentence 'Every year, my doctor ________ me to take a flu shot, but I refuse. So far, I have never had a virus.' is A. advises. Thus, the complete sentence should read 'Every year, my doctor advises me to take a flu shot, but I refuse.' The word 'advises' is appropriate here because it means that the doctor is recommending the flu shot as a preventative measure.
It is important to note that while getting an annual "flu shot" or influenza vaccine is highly recommended to reduce the chances of getting the flu, it does not guarantee that you will never contract the virus. The effectiveness of the flu vaccine can vary each year, as it is designed to protect against the most common influenza viruses expected in a given season.