|Question 13Verbal

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In economics, mustard seeds are considered a commodity because they are essentially interchangeable, "essentially" being a word that admits a degree of latitude. In 2021, researchers J. Shorish, M. Stephenson, and M. Zargham devised a mathematical model of fungibility (interchangeability) that would account for such variation. Distinguishing "exactly the same" and "nearly the same" commodities—whether crops, lumber, or precious metals—______ among their primary aims.
Which choice completes the text so that it conforms to the conventions of Standard English?
having been
A
being
B
was
C
were
D