In an interaction plot, sensitivity of the response to a factor is shown by the slope of the line for that factor setting. A steeper slope means the response changes more as Factor A moves from low to high, while a flatter line means the response changes less and is therefore less sensitive to Factor A. In the plot, the line labeled Factor B high rises noticeably as Factor A increases, indicating that when Factor B is high, the response is strongly affected by changes in Factor A. The line labeled Factor B low is essentially horizontal, meaning the response remains almost unchanged as Factor A moves from low to high. This indicates minimal sensitivity to Factor A at the low setting of Factor B.

This is an Analyze Phase interpretation of DOE interaction behavior. Black Belts use interaction plots to understand whether the effect of one factor depends on the level of another factor. Here, the least sensitivity occurs where the line is flattest. Therefore, the correct answer is C, Factor B low, because that setting makes the response least sensitive to changes in Factor A.