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题库 / OG2017V-SC-226
Around 1900, fishermen in the Chesapeake Bay area landed more than seventeen million pounds of shad in a single year, but by 1920, overfishing and the proliferation of milldams and culverts that have blocked shad migrations up their spawning streams had reduced landings to less than four million pounds.
that have blocked shad migrations up their spawning streams had reduced landings to less
that blocked shad from migrating up their spawning streams had reduced landings to less
that blocked shad from migrating up their spawning streams reduced landings to a lower amount
having blocked shad from migrating up their spawning streams reduced landings to less
having blocked shad migrations up their spawning streams had reduced landings to an amount lower
A, have blocked 时态错误
C. a low amount 不可数修饰 4m pounds可数，错误
D.having blocked 错了吗？
E. having blocked 错了吗？an amount lower错误同C
完成时态不可以做修饰成分，所以d,e错。
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