The method for making beer has changed over time.Hops（啤酒花），for example,which give many a modern beer its bitter flavor,are a（1） ____ recent addition to the beverage.This was first mentioned in reference to brewing in the ninth century.Now,researchers have found a （2） ____ ingredient in residue（残留物）from 5000-year-old beer brewing equipment.While digging two pits at a site in the central plains of China,scientists discovered fragments from pots and vessels.The different shapes of the containers （3） ____ they were used to brew,filter,and store beer.They may be ancient "beer-making tools," and the earliest （4） ____ evidence of beer brewing in China the researchers reported in the Proceedings of the National Academy of Sciences.To（5） ____ that theory,the team examined the yellowish,dried（6） ____ inside the vessels.The majority of the grains,about 80%，were from cereal crops like barley（大麦），and about 10% were bits of roots,（7） ____ lily,which would have made the beer sweeter,the scientists say.Barley was an unexpected find；the crop was domesticated in Western Eurasia and didn't become a （8） ____ food in central China until about 2，000 years ago,according to the researchers.Based on that timing,they indicate barley may have （9） ____ in the region not as food,but as （10） ____ material for beer brewing. A）arrived B）consuming C）direct D）exclusively E）including F）inform G）raw H）reached I）relatively J）remains K）resources L）staple M）suggest N）surprising O）test