Answer: A
Step-by-step explanation:
Domain is based off of the x-axis (left to right).
The curve starts at -1, and ends at 3. Therefore, x is greater than, or equal to -1, and x is less than, or equal to 3.
Also note that the dots signifying the beginning and end of the line is filled in (completely black). If the dot was not filled in, that's basically saying that line doesn't include the number the dot is on.
