At the tehran conference, the big three agreed on which overriding goal?
a. the need to bring a halt to the fighting
b. the need to invade the italian peninsula
c. the need to open a second front against germany
d. the need to invite hitler to future conferences

The correct option is C

The Tehran conference was a meeting that took place between November 28 and December 1, 1943, between the leaders Joseph Stalin, Winston Churchill and Franklin D. Roosevelt, who formed the Allied side. It constitutes one of the maximum exponents of cooperation of the allies in the Second World War.

It was the first conference between the three great ones (the Soviet Union, the United States, and the United Kingdom) in which Roosevelt was present, since he did not attend the Moscow conference, in August 1942. He succeeded the conference of Cairo and was followed by the Yalta conference and the Potsdam conference. The main debate focused on the opening of a second front in Western Europe.

this is a good question! i'll do some research and come back when i have the answer!