Native american slavery a. was a longstanding practice in new mexico. b. was considered wrong by american military. c. was never confused with adoption. d. was supported by president lincoln.

Its A

Explanation:

It was a longstanding practice in new mexico

alternative A.

Explanation: The military thought it was a lawful right to enslave Native Americans, so alternative B is a contradiction to this fact. There were some cases in which the ownership of Native American slaves, specially if they were young enough, was considered to be an adoption, so alternative C is incorrect as well. President Lincoln, stated on alternative D, was the one who freed the Native Americans from slavery, not supporting this kind of practice openly to the public. Then, the only alternative left was letter A, which stated that the slavery of Native Americans was a longstanding pratice in New Mexico. To be more precise, it was practised from 1850 to 1867, only stopped by law when it was considered to be illegal and it was banished in the whole country.

the answer is b your welcome : )

it was the first amendment