Final answer:
Obama uses allusion when he speaks about slaves singing freedom songs, as it refers to significant historical events without detailing them. Bravery and freedom are considered nonmaterial culture related to the American flag, representing the symbolic values it stands for.
Step-by-step explanation:
When Obama refers to slaves sitting around, singing freedom songs, he is employing the technique of allusion. An allusion is a brief and indirect reference to a person, place, thing, or idea of historical, cultural, literary, or political significance. It does not describe in detail the person or thing to which it refers. In this case, Obama is referencing the history of slaves singing songs about freedom, which carries deep cultural and historical significance and resonates with the experiences and emotions associated with the struggle for freedom.
In the context of the American flag, bravery and freedom are examples of nonmaterial culture. These ideas are associated with the flag but are not tangible. They represent the values, beliefs, and ideals that the flag symbolizes to many people. Hence, bravery and freedom, in this context, are symbols that contribute to the nonmaterial culture surrounding the American flag.