Your answer is going to be the second option, Triangle ABC was reflected across the y-axis and then translated 7 units down. To figure this out you can simply look at one of the points. For instance I looked at point C. The first thought is how do I get this point to the translated image? For C, it is at -3 so being reflected over the y-axis gets it to the translated image C' x value of 3. Then to move it down to where the translated image y value is, you have to go down 7 units.
Hope this helped!
