Answer:
The correct answer is c. That is 9 protein to form each facet
Step-by-step explanation:
Given that the capsids is 25-30nm in diameter and it contains 180 identical capsomeres, if the virus capsid has 20 facets in 180 capsomeres, then for each protein facet, it will contain 9 protein facets.
Thai is 180 capsomeres divided by total number of facets (20).