If the Quantity of Good a (Q_A)is Plotted Along the Horizontal

If the quantity of good A (Q_A) is plotted along the horizontal axis,the quantity of good B (Q_B) is plotted along the vertical axis,the price of good A is P_A,the price of good B is P_B and the consumer's income is I,then the slope of the consumer's budget constraint is __________.

A) -Qa/Qb
B) -Qb/Qa
C) -Pa/Pb
D) -Pb/Pa
E) I/Pa or I/Pb