At the level of the medulla oblongata, the "pacemaker" of normal breathing:Group of answer choicespneumotaxic centerDRGVRGapneustic center

The "pacemaker" of normal breathing at the level of the medulla oblongata is the Dorsal Respiratory Group (DRG).

Here's a step-by-step explanation:

1. The medulla oblongata is a part of the brainstem that plays a crucial role in controlling several vital body functions such as heart rate, breathing, blood pressure, and digestion.

2. Within the medulla oblongata, there are several groups of neurons that are involved in the control of respiration. These include the Dorsal Respiratory Group (DRG), the Ventral Respiratory Group (VRG), the pneumotaxic center, and the apneustic center.

3. The Dorsal Respiratory Group (DRG) is primarily responsible for initiating the basic rhythm of breathing. It sends signals to the muscles involved in inspiration (breathing in), causing them to contract and thus initiating a breath. This is why it is often referred to as the "pacemaker" of normal breathing.

4. The Ventral Respiratory Group (VRG) is involved in both inspiration and expiration (breathing out). It becomes active when a greater volume of air needs to be moved in and out of the lungs, such as during exercise.

5. The pneumotaxic and apneustic centers are involved in fine-tuning the rhythm of breathing, but they do not initiate the basic rhythm.

So, the answer to your question is the Dorsal Respiratory Group (DRG).