8. How does the author develop the idea that the causes of the flu are still a mystery? (RI.1.2) a. Scientists do not know how the flu is passed from birds to pigs to humans.
b. Scientists keep trying new techniques to increase the production of antibodies.
c. Even with the advances that have been made, the vaccines do not work all the time.
d. The scientists are sure another worldwide outbreak will never happen again.