1. Choose the correct answer:

As part of the investigation of Listeria monocytogenes outbreak, CDC workers checked the food histories of 20 patients infected with the outbreak strain and compared them with the food histories of 20 patients infected with other Listeria strains. This study design is best described as which one of the following:

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Analytical, experimental Analytical, observational, case-control Analytical, observational, cohort Descriptive