Final answer:
Roger loses his balance because the purse he attempts to steal from Mrs. Jones is unexpectedly heavy, causing him to fall.
Step-by-step explanation:
Roger loses his balance when he tries to steal Mrs. Jones's purse in "Thank You, M'am" because c. The purse is very heavy. When Roger attempts to snatch the purse, its unexpected weight throws him off balance, causing him to tumble. This encounter leads to unexpected kindness from Mrs. Jones, who, instead of reporting him to the police, takes Roger home, feeds him, and teaches him a valuable lesson about trust and respect.