From what I know, figure ABC has gotten smaller so you wouldn't use either options that suggests a dilation of 3, because that would mean it got bigger. (But please correct me if I'm wrong.) Also, if you look at the little unit square measurements on the graph, looking at figure ABC, C is 6 units from B, while in figure A'B'C', C' is 2 units from B', which 6÷2=3 meaning that A'B'C' would most likely be a third of its size.
Next the figure is being mirrored over the y-axis which is the vertical line going up and down.
So the answer would be the option that says
"Dilation by a scale factor of 1 over 3 followed by a reflection about the y-axis"
I hope that it's right, because I haven't practiced this in a while, and I hope this made some sense.