Final answer:
The Cuban official's comment on the Platt Amendment implies that the United States would control Cuba's affairs, as the U.S. was essentially given the 'keys' to the nation through the amendment.
Step-by-step explanation:
The best interpretation of the quote by the Cuban official regarding the Platt Amendment is that it signified the United States was going to control matters in Cuba. The quote metaphorically suggests that the United States held the 'keys' to Cuba, symbolizing significant authority and the potential for intervention 'at any time...whether with good or evil design.'
The Platt Amendment, an extension of the Teller Amendment, notably restricted Cuba's independence by placing various conditions on the newly formed nation, including granting the United States the right to interfere in Cuba's affairs to preserve its independence and, controversially, to establish a US military base at Guantanamo Bay.