Why was the rape of nanjing significant?
a. over 100,000 people were massacred.
b. it was a direct act of manipulation and terrorism.
c. the united states began to pay attention to japan s growing influence in the pacific.
d. it was significant for all of the above listed reasons.

The correct answer to your question would be D.
The Rape of Nanjing was significant because of the sheer volume of people who were massacred, because it was actually a direct act of manipulation and terrorism, these two things made also the United States more attentive towards the happening in the Pacific as it saw that the Japanese had an increased growth in influence over this region. 

Iwould say a, due to the fact these routes display many things that would be useful and provide explanations for how states are known.

Why do you have to ask such hard questions.