Amazon opens line-free grocery store in challenge to supermarkets

Amazon.com Inc said on Monday it has opened a brick-and-mortar grocery store in Seattle without lines or checkout counters, kicking off new competition with supermarket chains. Amazon Go, the online shopping giant's new 1,800-square-foot (167-square-meter) store, uses sensors to detect what shoppers have picked off the shelf and bills it to their Amazon account if they do not put it back. The store marks Amazon's latest push into groceries, one of the biggest retail categories it has yet to mast