The correct label of the line is option B. line CD.
How do we label a line?
In geometry, there are various ways to label a line, and the specific method used may depend on the context or the geometric representation. The common ways to label a line are as follows:
1. Single-letter notation: Lines are often labeled with a single lowercase letter. For example, a line might be denoted as "l" or "m." It's important to note that a line extends infinitely in both directions, so the letter is usually written with a double-headed arrow over it to indicate this infinite extension.
2. Two-point notation: A line can also be labeled by using two points on the line. The line is then named after these two points. For example, if points A and B lie on a line, the line can be denoted as AB or BA. Like in the given picture, points C and D lie on a line, then, the line can be denoted as CD or DC
3. Alphanumeric labels: In more complex geometric figures, lines may be labeled using alphanumeric combinations, especially when dealing with multiple lines. For instance, lines in a triangle may be labeled as sides AB, BC, and CA.
4. Function notation: In coordinate geometry, a line can be represented by an equation in the form y = mx + b, where m is the slope and b is the y-intercept. The equation itself can serve as a label for the line.