Given the task definition and input, reply with output. In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D". 

[header] How to test resistors [title] Remove power from the circuit containing the resistor. [step] This can be done by unplugging it from the mains or by removing the batteries if it is a portable device. Keep in mind that some devices still can be charged with a potentially harmful voltage until minutes after removing its power! [title] Isolate the resistor from the circuit. <sep> (A) [step] Refer to the instructions that came with your small electronic device. Select the power mark and remove power from the circuit. (B) [step] An attempt to measure a resistor that is still connected to the circuit can yield an incorrect calculation, as part of the circuit might also be measured. [substeps] Disconnect one end of the resistor from the circuit. (C) [step] This can take a while, depending on what you're plugging it into. Look on the side of the circuit board. (D) [step] Run a wire cutter or other tool over a resistor and then pull it away from the circuit using the tip of a screwdriver to remove the resistor. These don't have a wire cutter for this.

B