Pumpkins were among the many plant species from the Western Hemisphere introduced into the Eastern Hemisphere in the years following Christopher Columbus's first transatlantic voyage in 1492. This ongoing transfer of species between hemispheres _____ now known as the Columbian Exchange.
Which choice completes the text so that it conforms to the conventions of Standard English?
Explanation
Context: The sentence names what the movement of species between hemispheres is called today, and the blank holds that sentence's verb.
Answer: C) is
Why? The subject is the singular noun phrase "This ongoing transfer," so the verb must be singular, and the naming holds true in the present, as "now known as the Columbian Exchange" signals. "Is" meets both requirements. The plural "species" sits inside the modifying phrase "of species between hemispheres" and cannot govern the verb.
Traps:
- A) being → a participle rather than a finite verb, leaving the sentence a fragment.
- B) are → plural, agreeing with "species" instead of the singular subject "transfer."
- D) were → plural and past tense, clashing with both the subject and "now."