When the source of sound bulges or moves outwards, the air molecules present in that
space get pushed close to gether. This is known as a __________

Options

A. damping
B. rarefaction
C. compression
D. complete wave

Answer

**Step-by-Step Solution:**

1. **Understanding the Concept**: When a source of sound vibrates, it causes the surrounding air molecules to move. This movement can be described in terms of regions of high and low pressure.

2. **Identifying the Movement**: When the source bulges or moves outward, it pushes the air molecules together. This results in a region where the air molecules are closer than normal.

3. **Defining the Term**: The region where air molecules are pushed together is known as "compression." In contrast, when the source moves back, it creates a region where air molecules are spread apart, known as "rarefaction."

4. **Final Answer**: Therefore, the answer to the question is "compression."

---