If Good $x$ Is Measured Along the Horizontal Axis and Good $y$

Multiple Choice

If good $x$ is measured along the horizontal axis and good $y$ is measured along the vertical axis, then the slope of the budget constraint can be expressed as

A) - $P _ { x } / P _ { y }$
B) - $I / P _ { y }$
C) - $I / P _ { x }$
D) - $P _ { y } / P _ { x }$