What contributed to the end of the cuban missile crisis?
a. america's secret promise to remove missiles from turkey
b. soviet ships turning around rather than running the us blockade
c. castro's promise to restore democracy
d. castro's promise to break with the soviet union

The answer is letter b.  During this period the U.S. set up a blockade to prevent Russian ships from passing to Cuba.  The U.S. was alarmed after photos from a spy plane showed Russian missiles on Cuban soil.  This heightened American fears that Russia would invade through Cuba and use the missile already set up there.  At this point in time, the world was on the verge of nuclear war.  Both side weighed their options. After a tense period, secret negotiations brought an end to the conflict.  The Russians withdrew their missiles from Cuba and the U.S. withdrew their missiles from Turkey.

To be honest i thinks its between the first answer and the third answer