Shopping habits in America have changed a lot over the past few decades. Early ____ the 1900s most American towns and cities had a Main Street. Main Street was always in ____ heart of a town. This street was built with many stores on both sides. Shoppers walked into the stores to look ___ what they needed. ___, a change began to take place in the 1950s. Too many cars had crowded into Main Street while too __parking places were available(可用的) to shoppers. ___ the streets were crowded, shop owners began _____ look with interest at the open space from the city limits. When the first shopping center was built in the United States, an open space became _____ they first had considered.