A blood transfusion study shows:100 patientsTransfusion time range: 2.

According to the NAHQ CPHQ exam blueprint, histograms are the preferred tool for displaying distribution and frequency of continuous data.

Option A is correct because transfusion time is a continuous variable, and a histogram visually shows how values are spread across intervals.

Pareto charts rank categorical causes, control charts assess stability over time, and affinity diagrams organize ideas.

The CPHQ framework emphasizes selecting tools based on data type and analytic purpose, making histogram the correct choice.