Which part of a bow string indicates where the arrow is to be placed?

The nock locator is the correct answer because it is specifically designed to mark the position where the arrow is to be placed on the bowstring. This component ensures that the archer consistently nocks the arrow at the same point for improved accuracy and repeatability in shooting. By providing a fixed location, it helps to maintain the proper alignment and timing during the draw and release phases of shooting, which is essential for precision.

Other components like the kisser button, serving, and string silencer serve different purposes. The kisser button helps the archer achieve proper anchor points by providing tactile feedback when the archer's mouth touches it, helping to ensure a consistent draw. Serving refers to the winding around the bowstring to protect it and maintain its integrity, and string silencers are used to dampen the sound of the string when it is released. While each of these components is important for the overall functionality of the bow, the nock locator is specifically responsible for arrow placement.