Answer: D) I’m sorry that I can’t join you in your praise for the police department.
Step-by-step explanation: In the given passage from “Letter from Birmingham City Jail” by Martin Luther King, Jr, we can see that he expresses his disagreement with the praise for the police department to "keep order" and "prevent violence" because of the inhuman treatment that black people received from them. The statement that best identifies the main idea of the excerpt is I’m sorry that I can’t join you in your praise for the police department, because it summarizes the disagreement and disaproval.