For questions like these, what I like to do is plug in multiple points and see where they end up. I prefer simplicity, so I'll plug in a simple point -- x=3. If a or c was our graph, our y point would be at 3. As it is not, our options are left at b and d. For a square root, we know that 4 has a relatively simple square root, as its root is 2. To get 4 inside the square root box, x+3 must be equal to 4, so x=1. Plugging x=1 into both b and d, we get 2+3=5 and something else for d. Since y is not equal to 5 when x=1, b is incorrect and d is our answer. To ensure this, we could plug in a point for d. As we know that the cube root of 8 is 2, we could make sure that we have 8 inside the cube root box by making x equal to 5, and our y value would then be 2+3=5. As y=5 when x=5, these match up and d is our answer.
Feel free to ask further questions, and Happy Holidays!