Question in-kno
In knot theory (the mathematical study of curved, closed loops), knots are characterized by their crossing numbers—that is, the number of times the knotted thread crosses over itself. The trefoil knot and the figure-eight knot, each with a crossing number below five, blank among the simplest possible knots with the fewest number of crossings.
Which choice completes the text so that it conforms to the conventions of Standard English?
was
are
has been
is
In knot theory (the mathematical study of curved, closed loops), knots are characterized by their crossing
Hard-difficulty · SAT Reading & Writing · Boundaries — Coordination vs subordination for clarity. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.
Answer explanation
Choice B is the best answer. The convention being tested is subject-verb agreement. The plural verb "are" agrees in number with the plural compound subject "the trefoil knot and the figure-eight knot." The two types of knots joined by "and" function as a plural subject and thus require a plural verb.
Choice A is incorrect because the singular verb "was" doesn’t agree in number with the plural compound subject "the trefoil knot and the figure-eight knot." Choice C is incorrect because the singular verb "has been" doesn’t agree in number with the plural compound subject "the trefoil knot and the figure-eight knot." Choice D is incorrect because the singular verb "is" doesn’t agree in number with the plural compound subject "the trefoil knot and the figure-eight knot."
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