Final answer:
The solution to the equation 9x+4=9x+4 is infinite real solutions (D).
Step-by-step explanation:
The equation 9x+4=9x+4 does not have a solution because both sides of the equation are identical. When we subtract 9x from both sides, we get 4=4, which is always true. This means that any value of x will satisfy the equation. Therefore, the solution to the equation is infinite real solutions (D).