In this excerpt from president kennedy's 1963 civil rights address, he included the examples of president lincoln's efforts to end slavery and social and economic oppression for what purpose?

"one hundred years of delay have passed since president lincoln freed the slaves, yet their heirs, their grandsons, are not fully free. they are not yet freed from the bonds of injustice. they are not yet freed from social and economic oppression. and this nation, for all its hopes and all its boasts, will not be fully free until all its citizens are free."

to revise the definition of freedom
to explain the bonds of injustice
to explain the rights of heirs and grandsons
to explain the passage of time