A. both a cause of the changed relationship as well as one of the clearest illustrations of how startling the change had been
Incorrect
Both X as well as y is incorrect
B. both a cause of the changed relationship and one of the clearest illustrations of how startling the change has been
Correct
Best of all the options
The surge is a clear illustration of how startling the change has been. How startling the change was is not correct as the surge is still there.
C. both a cause of the changed relationship but also one of the clearest illustrations of how startling the change was
Incorrect
Both X but y - not correct
D. both a cause of the changed relationship and one of the clearest illustrations of how startling the change had been
Incorrect
Change happened because of a surge. And this surge is a clear illustration of the change.The change did not occur first . So past perfect is not needed.
E. both a cause of the changed relationship and one of the clearest illustration of how startling the change has been
Incorrect
it should be -One of the illustration
S.
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