Answer:
The Soviet Union invaded Afghanistan. and that created major tensions between the two world powers
Explanation:
During the Carter presidency, U.S.-Soviet relations were strained for several reasons.
Here is the major factor (in the context of the answer choices) that led to these tensions
Afghanistan invasion:
The Soviet Union invaded Afghanistan in December 1979, leading to a significant escalation of tensions between the U.S. and the Soviet Union.
There were other factors too but none of the other answers are correct