2017年6月英语四级（第1套 · 含听力）选词填空

Questions __26__ to __35__ are based on the following passage.
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 __26__ recent addition to the beverage. This was first mentioned in reference to brewing in the ninth century. Now, researchers have found a __27__ ingredient in residue (残留物) from 5,000-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 __28__ they were used to brew, filter, and store beer. They may be ancient "beer-making tools," and the earliest __29__ evidence of beer brewing in China, the researchers reported in the Proceedings of the National Academy of Sciences. To __30__ that theory, the team examined the yellowish, dried __31__ 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, __32__ 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 __33__ food in central China until about 2,000 years ago, according to the researchers. Based on that timing, they indicate barley may have __34__ in the region not as food, but as __35__ material for beer brewing.