Please answer this state 300 questions

Confounding: Researcher wanted to determine the long-term benefits of the influenza vaccine on seniors aged 65 or older. The research group looked at records of 36,000 seniors: Group 1 were seniors who chose to get a flu vaccine, Group 2 were seniors who chose not to get the flu vaccine. After observing the seniors for 10 years, it was determined that seniors who got flu shots were 27% less likely to be hospitalized for pneumonia or influenza, and 48% less likely to die from pneumonia or influenza. List some possible Confounding Variables (Are there characteristics that might influence the result that were not controlled for?):

3. Cellar phones and Cancer: Researcher Joachin Schuz wanted "to investigate cancer risk among Danish cellular telephone users". In 1995, his research group identified 420,095 people who first subscribed to a cell phone service between 1982 and 1995. In 2002, they recorded the number of people out of the 420,095 who had a brain tumor and compared the rate of brain tumors in this group to the rate of brain tumors in the general population. They concluded "cellular telephone use was not associated with increased risk for brain tumors." Is this an Observational Study or Designed Experiment?

Is it Cross-Sectional/Retrospective/Prospective?

4. Cavities: Xylitol is a food additive that has been tested in preventing dental caries (cavities). Unknown to the children, a total of 40 Peruvian children were given milk with xylitol and 35 children were given milk without xylitol. After one year of use, the number of cavities for the all subjects was recorded by dentists who were not informed of the children's groupings.

Is this an Observational Study or Designed Experiment? Is it Cross-Sectional/Retrospective/Prospective?