How did abbott, albert theories improve quality of life? ?

What is the answer to this particular question i have in health

The potential to eradicate preventable diseases in the future depends on other societal factors that influence coordination and deployment of global health resources. for example, 70 confirmed cases of circulating vaccinederived poliovirus type 2 (cvdpv2) were reported syria, which is embroiled in war. where else are similar societal challenges preventing the eradication of polio? uzbekistan. nigeria. pakistan. a and c. b and c.

Which one of the following causes people to go through a cycle of losing weight, gaining it back, then lose it again