This is from the commonlit article Thank You M’am Part C: Why does Roger want to thank Mrs. Luella Bates Washington Jones at the end of
the story?
A: Roger has grown to appreciate the faith that Mrs. Jones has in him.
B: Roger was suspicious of Mrs. Jones at first, but she shows him that people can
be trustworthy.
C: Roger appreciates that she did not report him to the police and wants to help
his family.
D: Roger realizes that Mrs. Jones invited him to her home because she is lonely and
wants his company.

The following act of  Roger that want to thank Mrs. Luella Bates Washington Jones at the end of  the story is as follows,

Explanation:

B: Roger was suspicious of Mrs. Jones at first, but she shows him that people can  be trustworthy.The main idea of Thank You, Ma'am is that it give lessons in what is right and what is wrong are appropriate if expressed in an environment of kindness.Mrs. Luella Bates Washington Jones wants to teach him a lesson about trust. She leaves the door open to her room, so he can enter at any time he wants to. That's the way she developed trust in Roger.Mrs. Luella Bates Washington Jones has every right to turn toward him in anger and even call for some form of justice. However, she welcomes Roger with utter compassion, to an extent of opening her home to him.