Historians also use terms like era and age. These are divisions of time that have no set number of years. Instead, they are defined by patterns or major events. The Bronze Age refers to a trend in the use of new materials. The time before the Bronze Age is called the Stone Age. The time after it is called the Iron Age. All three time periods are named for the material that were developed for tools and other objects. Based on the passage, which of these is most likely true? A Ages are longer than eras. B All eras have at least 1050 years. Bronze tools were popular in the Stone Age. D Bronze tools were in use before iron tools were used.