C. translated down 2 units
---The "-2" located on the outside of f(x) tells us that the y-values are being changed. With that, the graph can be moved up or down. The presence of the negative/subtraction sign tells us that the graph is moved down.
D. translated right 4 units
---The "-4" located with the x in f(x) tells us that the x-values are being changed. The only tricky thing about this is that the direction of the movement is actually the opposite of the sign. So with the negative/subtraction sign, the graph is moved to the right instead of the left.
Hope this helps!