Answer: Option d.
Step-by-step explanation:
To find the domain of the function we should look for the values for which the denominator is equal to zero, because the division by zero is not allowed.
We know by definition that the function is always greater than zero for all <em>x</em>.
We know that the constant <em>c</em> is greater than zero (c>0).
Then, the expression is never equal to zero.
Therefore, it does not exist a value for <em>x</em> that makes the denominator 0. Then, the domain of the function is all real numbers.
The answer is the option d.