Researchers investigate the association between the rate of hospitalzation from COViD-19 in peoplo who have diabetos. They found that having other ciseases (comorbidfies) in addition to diabetes increased the risk of hospitalization from COVID-19 and being immunized reduced the risk of hospitaizalion. i) What is the exposure in this study? ii) What is the cutcome of this study? ii) which factor modifies the relationstip between the exposure and the oulcome?.