## **Core Concept**
The cardiac cycle consists of several phases, including atrial contraction, ventricular contraction, and relaxation. Ventricular contraction, also known as systole, is the phase when the ventricles contract and pump blood into the pulmonary artery and aorta.

## **Why the Correct Answer is Right**
The ventricular contraction or systole can be divided into two phases: the isovolumetric contraction phase and the ventricular ejection phase. The entire systole lasts approximately 300-400 milliseconds (or about 1/3 of the cardiac cycle) at a normal heart rate of 70-80 beats per minute. This duration can vary based on heart rate and blood pressure.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately represent the duration of ventricular contraction in the cardiac cycle.
- **Option B:** This option is incorrect as it suggests a much shorter duration than what is physiologically accurate for ventricular contraction.
- **Option D:** This option is incorrect because it suggests a longer duration than what is typically observed for ventricular contraction.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the cardiac cycle's length and the duration of its phases change with heart rate. For example, with tachycardia (increased heart rate), diastole shortens more than systole. A useful approximation is that systole lasts about 1/3 of the cardiac cycle at normal heart rates.

## **Correct Answer:** C.