Be it enacted by the senate and house of representatives of the united states of america, in congress assembled, that it shall and may be lawful for the president of the united states to cause so much of any territory belonging to the united states, west of the river mississippi, not included in any state or organized territory, and to which the indian title has been extinguished, as he may judge necessary, to be divided into a suitable number of districts, for the reception of such tribes or nations of indians as may choose to exchange the lands where they now reside, and remove there; and to cause each of said districts to be so described by natural or artificial marks, as to be easily distinguished from every other

: what does the phrase indian title has been extinguished describe in the context of the document?

a: land the native americans had been granted
b: land that was taken away from native americans
c: land that was not valuable to the native americans
d: land that had been organized by the government