The graph shows a linear function that extends infinitely in both directions along the x-axis and y-axis. This means that the function has no restrictions on the values that x can take, as the line continues left and right without any breaks. Hence, the domain includes all real numbers.

The correct answer is:

A. All real numbers

Would you like more details on how to determine the domain of a function from a graph?

Here are 5 related questions:

1. What is the range of this linear function?
2. How do we find the slope of a linear function from its graph?
3. What is the equation of the line shown in the graph?
4. How would the graph change if the slope were steeper or flatter?
5. What are the characteristics of a linear function compared to other types of functions?

Tip: The domain of a linear function is always all real numbers unless there are explicit restrictions (like square roots or denominators).