Friction is caused by the _____ of the irregularities of two surfaces.

Explanation

To solve the question "Friction is caused by the _____ of the irregularities of two surfaces," we need to understand the concept of friction and how it relates to the surfaces in contact.

### Step-by-Step Solution:

1. **Understanding Friction**: Friction is a force that opposes the relative motion of two surfaces in contact. It arises when two surfaces interact with each other.

2. **Surface Irregularities**: Every surface, even if it appears smooth, has tiny irregularities or roughness at the microscopic level. These irregularities can be in the form of elevations (bumps) and depressions (indentations).

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