Answer:
Because the virus/sickness would evolve and that vaccine might not protect you.
Because flu viruses evolve so quickly, last year's vaccine may not protect you from this year's viruses. New flu vaccines are released every year to keep up with rapidly adapting flu viruses.
d. movement
Explanation:
take care :)
habitat
habitat is part of the ecosystem
niche describes ahow different organisms are linked
B he proved that the heliocéntrico model accurately described tour solar system
des
i think
