The correct answers are:
B) Britain and the U.S. would establish a second military front; and
C) If Bulgaria attacked Turkey, then Russia would come to Turkey’s aide and draw them into the war as an ally.
At the Tehran Conference, that was held in the Soviet embassy in Tehran between November 28 and 1 December 1943, Stalin and Roosevelt convinced Churchill to open a new front in France, in order to alleviate the pressure on the Eastern front. This would be the Operation Overlord, that would involve the D-Day landings in Normandy in June 1944.
Stalin also stated during the conference that, in case that Turkey was attacked by Bulgaria as a result of Turkey's involvement in the war against Germany, then the Soviet Union would instantly open a war against Bulgaria.