A reactive fetal heart tracing is defined by how many accelerations of at least how many beats per minute over the baseline that last for a minimum of how many seconds within 20 minutes?

A reactive fetal heart tracing is characterized by the presence of two or more accelerations of the fetal heart rate that meet specific criteria within a 20-minute monitoring period. Specifically, a reactive tracing demonstrates at least two accelerations, each of which must be a minimum of 15 beats per minute above the baseline and last for at least 15 seconds.

This definition aligns with criteria outlined in guidelines for fetal monitoring during pregnancy, emphasizing the importance of both the number of accelerations and the specifics of their duration and amplitude. Recognizing these patterns indicates that the fetus is likely receiving adequate oxygenation and is less likely to be experiencing distress.

In contrast, other options either misrepresent the required quantity of accelerations, the threshold for beats per minute, or the required duration, failing to encapsulate the standard definition of a reactive fetal heart rate tracing. Thus, option B correctly adheres to the established clinical standards for defining this important aspect of fetal monitoring.