Answer:
The correct option is B.
Explanation:
The slope of a line is calculated as
![m=(y_2-y_1)/(x_2-x_1)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/25uxp4sblay2143idvgkz738ukrk1vzo5g.png)
The slope of line is undefined if there is no change in the values of x. It is possible only in the case of vertical line.
Graph B represents a vertical line. So the slope of the line in graph B is
![m_B=\infty](https://img.qammunity.org/2019/formulas/mathematics/middle-school/96osjobl9im0buw4kwnn098wsd75ew0bln.png)
The slope of line B is undefined, therefore the correct option is B.