The phrase from the passage that provides context clues for the meaning of the word impetus is "desegregation across the country."
This is because the word impetus is a noun in which the phrase "desegregation across the country," modifies accordingly.
A noun phrase modifier is two or more words that illustrate or describe a noun.
Hence, in this case, it can be concluded that the phrase from the passage that provides context clues for the meaning of the word impetus is "desegregation across the country."
