The answer should be D. We see here he talks about peace through his speech.
Here I will highlight where he mentions his commitment.
"Looking back on the past with humility, I will not let the lesson learned from the tragedy of war fade with time and firmly maintain the antiwar pledge, dedicated to the construction of Japan as a peaceful nation."
A. rebuild Japan's superpower status. No. There is no mention of rebuilding it to become a superpower.
B. apologize to the families of the war dead. No. There is no apology here, just the promise of a peaceful future.
C. pay tribute to Japan's military heroes. No. There is no heart warming speech or tribute payed to the military heroes of Japan.
I hope I have helped! :)
