Final answer:
The domain of the step function g(x) = 4x + 3 is likely to be x is an integer, as step functions are typically defined at discrete points, such as integers.
Step-by-step explanation:
The domain of a function refers to the set of all possible input values (x-values) for which the function is defined. The graph of the step function g(x) = 4x + 3 suggests that it takes on values at certain specific points, commonly integers in the case of a step function. However, without an explicit restriction given in the question or a graphic representation to refer to, the typical domain of a linear function in the form of ax + b, where a and b are constants, would be all real numbers. If the given function g(x) is indeed a step function without further restrictions, the correct domain should be x is an integer, since step functions are defined at discrete points. Therefore, without additional context or a visual graph, the most likely answer would be option b) x is an integer.