Should Amazon be required to perform authenticity and safety on { none of, a few of, some of, a random sample of, all of } the items listed on their marketplace

Should Amazon be required to perform authenticity and safety on { none of, a few of, some of, a random sample of, all of } the items listed on their marketplace? Whole Foods often (always?) audits the supply chain of their products. Farmers’ markets sometimes audit the supply chain of their booths. Flea markets and eBay never do. What burden of audit should be placed upon Amazon?