well, if you ask me, and i assume you have. i would answer the a bomb qu, just because it may be wasier to talk about seeing as teh peace treaty one is largly political. you can talk about why te bomb was dropped, ie, russia (display might and end war quicky before russia could do anything signifigant on that front), truman, experimentation, overwhealming and unrealistic land invasion of mainland japan esp since the massive losses by allies at okinawa etc, then on consequenses, talk about russia the reaction (saw american might, couldnt claim that they had done much in teh war and tehrefore couldnt claim much territiory) that all i can think off teh top of my head. dunno if i helped, you could also talk about how the a bomb was teh catalyst of teh cold war, but i dunno what teh exact qu is.
good luck