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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
官方解释
续
A. The present-perfect tense of have blocked inappropriately describes an event that
caused something to happen before 1920. In addition, migrations up their
spawning streams is incorrect.
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