Instructions: 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".
Input: [header] How to clean an imac screen [title] Shutdown and unplug your imac. [step] Click the apple icon in the upper left corner of your imac screen. Then click " shut down. <sep> (A) " if you have an ios device older than the ios 6.7 os or bigger, this can be done by clicking " apple device manager " or clicking " devices " from your device's dock. [substeps] Turn off the device you're going to use the cleanest find-appropriate system cleaner. (B) " turn off your apple screen (which you have accessible through your ios device). [substeps] If you don't have an ios device, you can plug one end of the usb cord into the port on the outside of your ios device. (C) " unplug the power cord from the back of your imac. [substeps] Additionally, unplug any other devices that are connected to your imac like speakers and hdmi cords. (D) " [title] Press and hold the power button. [step] Once it turns off, press and hold the power button until the apple logo appears.
Output:
C