Which sentence is punctuated correctly?
A: Ralph Waldo Emerson once said, A foolish consistency is the hobgoblin of little minds.
B: Ralph Waldo Emerson once said, A foolish consistency is the hobgoblin of little minds.
C: Ralph Waldo Emerson once said, “A foolish consistency is the hobgoblin of little minds.”
D: Ralph Waldo Emerson once said, ‘A foolish consistency is the hobgoblin of little minds.’