Left and right motion indicates change in x-value.
If we subtract 6 from the x-coordinate of each point,
A(3, 4) will be transferred to A'(3-6, 4) = A'(-3, 4).
B(4, 0) will be transferred to B'(4-6, 0) = B'(-2, 0).
C(2, 1) will be transferred to C'(2-6, 1) = C'(-4, 1).
Hence, the correct option is c. Δ ABC is congruent to Δ A'B'C' because you can mapΔ ABC to Δ A'B'C' using a translation 6 units to the left, which is a rigid motion.