31. According to the passage, it is NOT true that flu vaccines:
Your Answer is
Correct Answer is D
Explanation
Option D is a wrong statement, because flu vaccine cannot prevent the occurrence of influenza, it can only treat and control influenza after it appears;
Option A: lines 9-13 indicate that flu vaccine needs It is updated every year;
Option B: lines 10-13 indicate that it is based on the predictions of scientists;
Option C: lines 24-25 indicate that flu vaccine may only be effective for that year effective for flu species;