Sentence Correction (SC) | Re: Since 1998, when the first direct discovery of so-called dark energy

Zhanbo is on point in explaining why the correct answer choice is D.

I would just add to the way one should look at the sentence while answering.

Since 1998, blah blah , modifier , and blah blah , modifier , other tools .

Here if we strick out everything after 1998 and before other tools it shortens the paragraph and helps to look at the things that matter.

Now since have two usages.

Since can be used as because , or since in reference to time.

Eg. I am not able to work , since I am suffering
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