Smallpox is a virus that causes a rash that then turns into painful blisters. the last known case of smallpox was in 1977. what is the best explanation for the eradication of smallpox? people are exercising more than they used to. genetic testing determines who is more prone to smallpox. there was an increase in antibacterial products. a vaccine was developed.

The correct answer would be a vaccine was developed.

A vaccine is a substance (usually a heat-killed or attenuated pathogen or antigen) which is injected into the body of the person in order to produce antibody and thus it develops immunity against that specific pathogen or disease.

A vaccine for smallpox was developed in 1796 by Edward Jenner which results in global eradication of smallpox.

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.