Who agrees to an immigrant become a citizen

It must be a U.S. citizen or a permanent resident of the United States of America.  That person must also subsidize the petitioner as well.  They have to prove that the petitioner is not inadmissible or becomes a public charge who asks for benefits from the government.  The sponsor must prove that they are financially capable of supporting the petitioner or they will be the ones paying the government when they request benefits.

the answer is the last one

you need to make an explanation. so, since you did not include one, so no one, and i mean no one can unfortunately you,