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

ANS:D - 12 k

@All.

First understand the question.

For voltage divider circuit, V_out=V_in×(R2/(R1+R2)); R2-Load resistance to be changed. If we assume V_in=50V.
For R2=1Mohm, V_out~49V.
For R2=18Kohm, V_out=30V. For R2=12Kohm, V_out=25V.

That's why, 12Kohm resistance has the most reduction in output voltage.

So it affects more. I hope you will understand.