Read the short historical news article and answer the following question: based on the information in the article, which statement must be true?

cuba has long been an ally of the communist soviet government. recently, it announced plans to expand its military defense capabilities. soon after, u. s. government spy planes took photos of what appeared to be soviet missile installation sites on the island of cuba. president john f. kennedy then issued a statement that the behavior of the soviet government could be considered an act of war. the soviet leader, nikita khrushchev, responded to kennedy's statement with his own, claiming that "any action on the part of the u. s. government to interfere with cuban affairs will be considered an act of war." neither leader has issued a statement since. however, two days after khrushchev's statement, by the orders of the president, the u. s. navy dispatched part of its fleet to set up a blockade that will prevent further delivery of soviet missile equipment to cuba.

a.
khrushchev's statement was caused by the u. s. government taking photos of cuba.

b.
the spy plane photos caused the united states to issue a statement about the soviet union.

c.
u. s. spying caused cuba to want to increase its military defense capabilities.

d.
president kennedy's order to set up a blockade was caused by the cuban announcement.