**Core Concept**
A QRS duration between 100 and 120 milliseconds is considered within the normal range. This duration represents the time it takes for the ventricles to depolarize and is a key parameter in the assessment of cardiac conduction.

**Why the Correct Answer is Right**
A QRS duration of 100-120 milliseconds suggests that the ventricles are depolarizing normally, without any significant delay or blockage of electrical conduction. This is because the duration is within the normal range, indicating that the electrical impulse is being conducted through the ventricles without any significant issues.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because a QRS duration of 100-120 milliseconds is not indicative of a left bundle branch block (LBBB), which typically has a wider QRS duration (>120 ms).
**Option B:** Incorrect because a QRS duration of 100-120 milliseconds does not suggest a right ventricular hypertrophy (RVH), which can be associated with a left axis deviation and a QRS duration that is often within normal limits.
**Option C:** Incorrect because a QRS duration of 100-120 milliseconds does not indicate a ventricular pre-excitation syndrome, such as Wolff-Parkinson-White (WPW) syndrome, which typically has a short PR interval and a wide QRS complex.

**Clinical Pearl / High-Yield Fact**
A QRS duration of 100-120 milliseconds is considered normal, but it's essential to consider other ECG parameters, such as the PR interval, QRS axis, and T wave morphology, to evaluate the overall cardiac conduction.

**Correct Answer: None, as all options are incorrect.**