For the following question, arrange the sentences A, B, C, and D between sentences 1 and 6 to form a logical sequence with sentence 1 and sentence 6 as the starting sentence and the concluding sentence respectively:
(1) Once upon a time, a rat lived on the bank of a river.
(A) A dog, who lived near the bank, saw the rat.
(B) Spotting a chance to save a life, he jumped into the water.
(C) One day, it accidentally fell into the water.
(D) He saw that all the efforts of the rat to stay afloat were failing.
(6)
The rat was thus rescued.