256. During an era when interracial tensions in the United States have run high, Rosa Parks became a quiet, unassuming symbol of the continued struggle for human dignity.
(A) have run high
(B) ran high
(C) had run highly
(D) run high
(E) were running highly
Please explain your answers.
Excluded A and C: don't need had / have in any answer b/c "interracial tensions" did not do two separate things in the past.
Excluded D: indicates that the interracial tensions continue today--not the case.
Excluded E: would dismiss right away b/c "running highly" is awkward
Left with B. Correct past tense