Answer: C. The emotion in Ms. Graps's voice as she talks about her search for her son.
A telling detail is a piece of information that, even though it appears to be small, in fact illustrates the point that the author is trying to make. A telling detail is usually descriptive, emotional and illuminating. It should also be unique. In this case, the emotion with which Ms. Graps speaks illustrates how hope survives among Katrina's survivors.