Leaching, the recovery of copper from the drainage water of mines, as a method of the extraction of minerals, it was well established as early as the eighteenth century, but until about 25 years ago miners did not realize that bacteria take an active part in the process.
gwd-1-41 Leaching, the recovery of copper from the drainage water of mines, as a method of the extraction of minerals, it was well established as early as the eighteenth century, but until about 25 years ago miners did not realize that bacteria take an active part in the process. A. as a method of the extraction of minerals, it was well established B. as a method of the extraction of minerals well established C. was a well-established method of mineral extraction D. was a well-established method of extracting mineral that was E. had been a method of mineral extraction, well established
这道题,答案是C,说Dthat was 多余,我就是不明白怎么多余了,没有that was来引导时间状语,as early as又能和谁平行呀?
我觉得有了D的that was ,我们才可以认为that was (a period) as early as the eighteenth century,而不是C中mineral extraction as the eighteenth century
这里as early as 没有在追求平行这个结构吧? 它意思不就是 “早至18世纪” 去掉中间插入语 Leaching was a well-established method of mineral extraction as early as the eighteenth century, blahblahblah