Directions: The given sentence is divided into four parts A, B, C, and D. Choose the part that contains an error as your answer. If the sentence is error-free, mark 'No error' as your answer.

Scarcely had the sun dipped below the horizon (A) than the ethereal hues of twilight began to envelop the sky, (B) casting an enchanting gradient of purples and pinks across the tranquil landscape, (C) infusing the world with a sense of ephemeral beauty that left observers awestruck and contemplative. (D)