What technique should be used to perform chest compressions on a child weighing 42 pounds?

In performing chest compressions on a child weighing 42 pounds, the technique that utilizes one hand on top of the other, interlaced, is appropriate and effective. This method allows for deeper and more controlled compressions, which are essential for maintaining blood flow during cardiopulmonary resuscitation (CPR).

When applying this technique, it's important to use both hands to generate sufficient force, particularly for a child of this weight, ensuring that the compressions are both adequate in depth and rate. This technique is suitable for children over the age of one, where the rescuer’s hand size and strength can make a significant difference in delivering compressions that are effective in generating blood circulation.

Other options, like the use of one or two fingers, are typically reserved for infants or very small children, where the rescuer might not have the strength or the appropriate hand size to perform effective compressions. Placing hands on the stomach is not a recognized technique for performing chest compressions and would not provide the necessary support for cardiac function during an emergency. Thus, the interlaced hand technique is the most effective and recommended approach in this scenario.