Question

What is the domain of his graph?

Answer 1

Domain represents all of the values that "x" can be.
In the illustration above, x represents time. Can time be negative? (No - unless you have a time machine!).  So the smallest value that x can be is 0.
Now let's look at what happens when x is greater than 8....the y-value would be negative.  In the illustration above, y represents depth. Can depth be negative? (No!)  So the largest value that x can be is 8.

Answer: B. Real numbers from 0 to 8