Question

triangle abc is congruent to △abc by the hl theorem
what single rigid transformation maps △abc onto △abc?
dilation
reflection
rotation
translation

Explanation:

A reflection is a rigid transformation that flips a figure over a line (here, the line could be the vertical line through point \(B\)). A dilation changes the size (not rigid). A rotation turns a figure around a point (no indication of turning here). A translation slides a figure (no sliding - flipping over a line is key). Since \( \triangle ABC\) and \( \triangle A'BC'\) are mirror - images across a line (implied by the congruence via HL and the figure's symmetry), reflection is the correct rigid transformation.

Answer:

B. reflection