**Core Concept**
The sternum is depressed at a rate of 5-7 cm (2-3 inches) during CPR to facilitate effective chest compressions, allowing for the optimal delivery of oxygen to the heart and brain. This technique is crucial in maintaining blood flow and perfusion during cardiac arrest.

**Why the Correct Answer is Right**
The American Heart Association recommends a compression rate of 100-120 compressions per minute, with a depth of 5-7 cm. This is because optimal coronary perfusion pressure is achieved with a compression depth of 5-7 cm, which allows for adequate blood flow to the heart muscle. The rate of compression is also critical, as both under- and over-compression can lead to decreased cardiac output and increased myocardial damage.

**Why Each Wrong Option is Incorrect**
**Option A:** 3-4 cm - This depth is too shallow and would not provide adequate compression of the heart.
**Option B:** 10-12 cm - This depth is too deep and could lead to rib fractures and other complications.
**Option C:** 50-60 compressions per minute - This rate is too slow and would not provide adequate blood flow to the heart and brain.

**Clinical Pearl / High-Yield Fact**
Remember the "30:2" ratio for CPR: 30 chest compressions followed by 2 rescue breaths. This ratio ensures optimal ventilation and perfusion during cardiac arrest.

**Correct Answer:** C. 100-120 compressions per minute with a depth of 5-7 cm.