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Could you please take a look at this question?
https://gmatclub.com/forum/around-1900- ... l#p2520376Q1. I have some question on the chronological sequence of the correct choice.
Around 1900, fishermen in the Chesapeake Bay area landed more than seventeen million pounds of shad in a single year, but by 1920, over-fishing and the proliferation of milldams and culverts that blocked shad from migrating up their spawning streams had reduced landings to less than four million pounds.Does the underlined portions imply that: blocking (in simple past) appeared AFTER the reduction (past perfect)?
I think this sequence doesn't make sense at all.
You've probably heard that the past perfect is used for something that occurred in the past, BEFORE
another action, event, or time marker occurred in the past. In evaluating this sentence, we need to see whether the use of past perfect is correct by attempting to find this secondary action/event/time marker in the past.
It's tempting to see the word "blocked" and think, "heck yes, there's my simple past time marker!" The problem is that not every -ed word is a verb (more -ed word fun can be found
here). In this case, "blocked" is not actually a verb: it's an -ed modifier, and in this sentence is just modifying "milldams and culverts". So, "blocked" is not expressing an action/event/time marker in the past, and we don't have to evaluate whether it would work as the event AFTER our past perfect verb.
Instead, look elsewhere in the sentence to find this marker. You'll see that the clause begins with a time stamp, "by 1920." This is a perfectly acceptable time marker in the past, and in conjunction with our main verb ("had reduced"), the sentence tells us that the reduction happened before 1920. So, the past perfect works in this sentence.
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Q2. Why is choice A. wrong?
Why is present perfect tense wrong here?
Why is it illogical to say that blocking started in the past and remains in effect today?
"Milldams and culverts" are long-lasting infrastructure. So, IMO, it makes sense to say that the blocking is still relevant in the present context.
Remember, the main action of the clause, "had reduced," happened before 1920. "Blocked" is part of a phrase describing the thing responsible for this past reduction. So while there's no way to know if the milldams and culverts are still blocking fish, it's the blocking that occurred
in the past that we care about.
Consider another example:
"Tim, who ruined Christmas by forgetting to buy presents for his children, was in the doghouse."
Could you argue that Tim is still ruining Christmas to this day? Sure. And knowing Tim, that's probably a safe assumption. (To say nothing of New Year's Eve and Valentine's Day and Saint Patrick's Day, etc.) But "was" is a past tense verb, so it makes sense to keep the act of ruining Christmas in the past tense, too.
I hope that helps!
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