The method for making beer has changed over time. Hops, for example, which give many a modern beer its bitter flavor, are a _____(26)recent addition to the beverage. This was mentioned in reference to brewing in the ninth century. Now, researchers have found a _____(27)ingredient in residue(残留物) from 5000-year-old beer brewing equipment. While excavating two pits at a site in the central plains of China, scientists discovered fragments from pots, funnels, amphorae, and stoves (stove fragment pictured). The different shapes of the containers _____(28)they were used to brew, filter, and store beer.They may be ancient “beer-making toolkits,” and the earliest _____(29)evidence of beer brewing in China, the researchers report online today in the Proceedings of the National Academy of Sciences. To _____(30)that hypothesis, the team examined the yellowish, dried _____(31)inside the vessels. The majority of the grains, about 80%, were from cereal crops like millet and barley(大麦), and about 10% were bits of roots, _____(32)likely, 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 _____(33)food in central China until about 2000 years ago, according to the researchers. Based on that timing, they suggest barley may have _____(34)in the region not as food, but as_____(35)material for beer brewing beer.