Angle Classification: Identify the Type of ∢ABC in Geometric Notation

To determine the type of angle $\angle \text{ABC}$, we will consider the following:

• Step 1: Observe the positions of points A, B, and C, which are depicted in the diagram as lying on a straight line.
• Step 2: Recognize that when three points lie on a straight line and a central point (B here) is between two others (A and C), it forms a flat angle.
• Step 3: Recall that a flat angle is defined as an angle that measures $180^\circ$, which is the total rotation a line undergoes around a single point.

Visual inspection of the diagram confirms that points A, B, and C create a straight line. Hence, the angle $\angle \text{ABC}$ must be a flat angle.

Therefore, the angle $\angle \text{ABC}$ is a flat angle.