Answer: Figure A
Explanation:
We know that in reflection every point on the figure and its corresponding image point are equidistant from the line of reflection.
When we reflect a figure across the y-axis, then the y-coordinates of the points of the pre-image remains the same, but the x-coordinate is transformed into its opposite.
The given line of reflection is y-axis.
The only figure which follow the rule of reflection across y axis is figure A because in figure A the vertices of triangle ABC and the corresponding vertices of equidistant from y-axis.