The Answer is B i just took the test. Enjoy, i also just looked it up on a quizlet. That's another website you can use if it comes up in the search for the question.
Designing efficacious norovirus vaccines remains a major challenge due to several factors:
(1) the extreme genetic variability within the norovirus family and within genogroups
(2) the rapid evolution of antigenically dissimilar pandemic GII.4 norovirus strains
(3) the lack of lasting immunity upon natural exposure to noroviruses in at least a proportion of the population.
Answer:
ok tell me
Explanation:
i can edit this so once you tell me i can change it
Depends, if it's from acid rain (or acid from plants) its chemical if it's from the wind beating (or a plants roots) it down then its physical
