Answer:
A). Assonance
Step-by-step explanation:
Assonance is characterized as the literary device in which the author employs a 'repetition of similar or identical vowel sounds usually with distinct consonants' to lay stress on specific syllables and emphasize the message.
In the given excerpt form former U.S. president Barack Obama's 2009 inaugural address, assononance has been employed as the vowel 'e'(in 'citizens, seared, memory, we, well, liberty') and 'o'(in our, memory, those, lost, know, too, etc.) have been constantly repeated to highlight the speaker's intention that neither he nor his people will forget 'what they have lost.'