Answer:
Correct answer is d. all of the above.
Step-by-step explanation:
Relations between two countries were pretty tense, especially during the period when Fidel Castro was dominant figure in Cuba.
But everything changed during the presidency of Barrack Obama.
In 2014 it was announced that two countries will reestablish their embassies and then in 2016 Obama visited Cuba.
This led to further liberalization between two countries, which included the travel restrictions.