D-day was important because it:

a. ended the war in the pacific.

b. was the day hitler surrendered.

c. opened up a second front in europe.

d. stopped the nazi advance in eastern europe.

C. opened up a second front in europe

to protect the united states' role as a world leader, president truman wanted to prevent the soviet union from spreading communism beyond its post-world war ii boundaries. he declared that the united states must assist any nations struggling to prevent a communist takeover.