Final answer:
The sequence exhibits congruence between triangles Δefg and Δe'f'g' when it slows down between points a and d and between points e and h, and speeds up between points d and e and then again after point i.
Step-by-step explanation:
A sequence that exhibits the congruence between triangles Δefg and Δe'f'g' can be described by statement b. According to statement b, the sequence is slowing down between points a and d, and between points e and h. It is speeding up between points d and e, and then again after point i.