Answer: Choice A.
![x \le 0](https://img.qammunity.org/2021/formulas/mathematics/middle-school/820nv44gn4twwmmm5hipkpg9yv7dhgn6di.png)
x can be any number smaller than 0, or it can be equal to 0 itself.
This is because the furthest to the right we can go is at x = 0. This endpoint is included due to the filled in circle at the endpoint.
There is no left boundary, so the graph goes on forever toward negative infinity.
We can say
but it's easier to say
![x \le 0](https://img.qammunity.org/2021/formulas/mathematics/middle-school/820nv44gn4twwmmm5hipkpg9yv7dhgn6di.png)
The domain in interval notation would be
. The square bracket says "include this endpoint". The curved parenthesis means "exclude this endpoint". We cannot reach either infinity, so we always use a curved parenthesis with either infinity.
As implied, the domain is the set of all possible x values of a function. The range is the set of all possible y values.