Explanation:

Let's go through each sentence and option to find the correct order:

- C: A dog and a cock having struck up an acquaintance went out on their travels together.

- This sentence introduces the main characters.

- D: Nightfall found them in a forest, so the cock, flying up on a tree, perched among the branches, while the dog dozed below at the foot.

- It follows logically after C, describing the actions they took when night came.

- B: As the night passed away and the day dawned, the cock, according to his custom, set up a shrill crowing.

- This occurs after they have been settled for the night, leading into morning activities.

- A: A fox, hearing the cock and thinking to make a meal of him, came and stood under the tree.

- This introduces a new character and a problem, prompted by the cock's crowing.

Option 2: DCAB is the correct order of the sentences:

- C: Start with the introduction.

- D: Set the scene and actions for nightfall.

- B: Morning arrives and the cock crows.

- A: The fox arrives in response.

Correct Answer: Option 1