Answer:
A and D
Explanation:
To find f + g, you can add both functions together, which results in the following:

The domain is all real numbers is correct because you can substitute any x-values and have y-values.
The range of all real numbers is false because some x-values cannot be evaluated to a certain y-value. An example is when y = 0, no x-values satisfy the condition when y = 0.
It is a linear function is false because a linear function is defined as y = mx + b, only one-degree. However, the following function is second-degree, so it cannot be linear.
It is a quadratic function is correct because a quadratic function is defined as y = ax² + bx + c, the second-degree. Since the function has the highest degree of 2, thus, it is a quadratic function.