What event prompted a massive wave of “sit-ins” across the country? a

What event prompted a massive wave of “sit-ins” across the country?

a. African Americans went on a hunger strike after being refused service at a diner.
b. An African American soldier refused to stand and salute an abusive white officer.
c. A white restaurant owner assaulted a black customer when she asked to be served in a white area.
d. Three African American college students refused to leave a lunch counter after being denied service.
e. Three African American women refused to get off a bus after being asked to move to the back.

ANSWER
D