What is the domain of f(x) = 3 square root x?

The correct option is A) all real numbers.

Step-by-step explanation:

Consider the provided function.

Domain of the function is the set of input values which a function can take or the domain is the set of all possible x values which a function can take.

Now consider the provided function.

The above function can take any value of x and defined for all real numbers.

The graph of the above function is shown in figure 1.

Now if we observe the graph of the function we can concluded that the function is defined for any value of x.

Also the function is continues everywhere on the real number line.

Hence, the domain of the provided functions is all real numbers.

Thus, the correct option is A) all real numbers.