Question

add a comma or semicolon if needed. otherwise, submit the text without any additional punctuation.
a flock of starlings, turning and twisting through the sky together, is called a murmuration □ hundreds or even thousands of birds seem to move in unison.

Explanation:

The sentence "A flock of starlings, turning and twisting through the sky together, is called a murmuration hundreds or even thousands of birds seem to move in unison." has a missing comma after "murmuration" to separate the appositive or the descriptive phrase. The correct sentence should be "A flock of starlings, turning and twisting through the sky together, is called a murmuration, hundreds or even thousands of birds seem to move in unison." (Note: Alternatively, a semicolon could be considered, but a comma is a simpler punctuation here to separate the parts of the sentence for clarity. However, actually, a semicolon might be more appropriate to separate two independent clauses, but the initial instruction is to add a comma or semicolon if needed. Let's re - evaluate: "A flock of starlings, turning and twisting through the sky together, is called a murmuration" and "hundreds or even thousands of birds seem to move in unison" are two independent clauses. So a semicolon would be better, but the instruction says comma or semicolon. But the blank is after "murmuration", so we add a comma (or semicolon). Let's go with comma as per the instruction's option of comma or semicolon. So the text with the added comma is "A flock of starlings, turning and twisting through the sky together, is called a murmuration, hundreds or even thousands of birds seem to move in unison."

Answer:

A flock of starlings, turning and twisting through the sky together, is called a murmuration, hundreds or even thousands of birds seem to move in unison.