Answer:
Correct answer is A)The missiles were so close to the U.S., giving the Soviet Union a nuclear advantage .
Step-by-step explanation:
A is the correct answer as the missiles were located less than 100 hundred miles away from United States and presented a real threat for the safety of the country.
B is not correct as the missiles were kept in secret there.
C is not a correct answer as officially war was not declared, although situation was really tense.
D is not correct as this planes were the ones that discovered the existence of nuclear missiles. And, yes a spy plane was shot down.