The analog input channel voltage range for a PIC$16$ Microcontroller is limited to the positive range $0-$Vref. Many situations require a digitized mapping from bipolar analog signals to unipolar signals. A simple resistive network has been designed to translate a bipolar voltage range of $-6$ V to $+6$ V to a unipolar range of $0-2\mathrm{.}5V,$ assuming Vref is $+2\mathrm{.}5$ V $.$ A reasonable resistor combination is:

a$.2\mathrm{.}5,3\mathrm{.}5,$ and $5$ Kohms

b$.1\mathrm{.}46,2\mathrm{.}5,$ and $3\mathrm{.}5$ Kohms

c$.$ None of them

d$.1\mathrm{.}5,2\mathrm{.}5,$ and $5$ Kohms