Answer:
The detail from the excerpt that best helps the reader determine a tone of alarm is "Mr. Morrison never made sounds like that."
Step-by-step explanation:
The speaker was in silent recitation when she was interrupted by a tapping on the porch. So far, there is nothing that conveys a sense of alarm. A tapping on the porch could be a normal, expected occurrence, especially if it is a sound the speaker can recognize. What really determines a tone of alarm is the fact that the speaker lays very still because she does not recognize the sound. It is a sound Mr. Morrison never made. It is with this information that we get to know there is something strange, suspicious, and alarming about the tapping on the porch.
"Roll of Thunder, Hear My Cry" is a novel by author Mildred D. Taylor. It discusses racial issues during the Great Depression through the eyes of the narrator and main character, Cassie Logan.