Which of the following functions has a range of all real numbers? a. y=-3(5^x) b. y=x^2-3 c. y=6x+4 d. y=2(2^x)

Only the function in C has the range of all real numbers.
Later on, when you will be familiar with more type of functions you will know that when x is on the power range is usually only positive values or negative values if only not shifted, even if shifted it will only add to its range this numbers by which unit it was shifted.
B is shifted parabola. It has the range of  {y| -3≤∞}