A certain voltage divider consists of two 12 kΩ resistors in series. Which of the following load resistors will have the most effect on the output voltage?

For two resistors in series

R1 = 12 kohm + 12 kohm =24 kohm

As voltage divider formula is given as

Vout = Vin × (R2 / R1+R2)

Vout /Vin = R2/R1+R2

For most effect Vout/Vin should be minimum i.e. value of R2 should be as low as possible.

Thus, R2 = 12 kohm