OG16 verbal分册 SC38

virnnie · 发表于 2015-10-19 18:28:46

[size=15.000000pt]Around 1900, fishermen in the Chesapeake Bay area landed more than seventeenmillion pounds of shad in a single year, but by 1920, overfishing and theproliferation of milldams and culverts that have blocked shad migrations up theirspawning streams had reduced landings to less than four million pounds.
[size=15.000000pt](A) that have blocked shad migrations up their spawning streams hadreduced landings to less
[size=15.000000pt](B) that blocked shad from migrating up their spawning streams hadreduced landings to less
[size=15.000000pt](C) that blocked shad from migrating up their spawning streams reducedlandings to a lower amount
(D) having blocked shad from migrating up their spawning streams reducedlandings to less
[size=15.000000pt](E) having blocked shad migrations up their spawning streams had reducedlandings to an amount lower
[size=15.000000pt]

正确答案B。
这里比较的不是说1920年前和1920年后吗？by 1920就是说直到1920年，shad的数量已经下降到少于4 million pounds了。那么显然这个应该是发生在1900年之后啊，为什么能用had done？是强调影响吗？
另外，为什么不能选择D？OG解释说，having blocked shad from....要用逗号隔开，为什么要用逗号隔开？

morimori · 发表于 2015-10-19 20:34:59

had done要和过去时间点一起出现，表示过去的过去，而这里的by 1920就是那个过去的时间点，所以用had done，表示在1920年以前，shad的数量就已经下降到4m。

D的话除了时态错误以外，having done是不可以做限制性定语的，这是为什么og说一定要用逗号隔开的原因。

virnnie · 发表于 2015-10-19 21:11:29

morimori 发表于 2015-10-19 20:34
had done要和过去时间点一起出现，表示过去的过去，而这里的by 1920就是那个过去的时间点，所以用had done ...

感谢！懂了！

sylviah · 发表于 2016-9-26 15:37:06

另外og说 A选项的migrations up their spawning streams 这种表达是错的，为什么？我的理解是，up their spawning streams修饰migrations，这样不可以？

OG16 verbal分册 SC38

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