correct the verb tense error in sentence three.

The stretch of road was almost 500 yards long, completely arched over with huge, wide-spreading apple trees, which have been planted years ago by an eccentric farmer. Overhead was one long canopy of snowy fragrant bloom. Below the boughs, the air was full of purple twilight, and far ahead a glimpse of painted sunset sky shines like a great rose window at the end of a cathedral aisle.

The correct verb tense should be "had been planted" to indicate that the planting occurred in the past before the action of the sentence.

The corrected sentence is: The stretch of road was almost 500 yards long, completely arched over with huge, wide-spreading apple trees, which had been planted years ago by an eccentric farmer. Overhead was one long canopy of snowy fragrant bloom. Below the boughs, the air was full of purple twilight, and far ahead a glimpse of painted sunset sky shone like a great rose window at the end of a cathedral aisle.

The stretch of road was almost 500 yards long, completely arched over with huge, wide-spreading apple trees, which had been planted years ago by an eccentric farmer. Overhead was one long canopy of snowy fragrant bloom. Below the boughs, the air was full of purple twilight, and far ahead a glimpse of painted sunset sky shone like a great rose window at the end of a cathedral aisle.

The verb tense error in sentence three is in the phrase "which have been planted years ago by an eccentric farmer." To correct this error, we need to adjust the verb tense to match the rest of the sentence.

The corrected sentence should read: "The stretch of road was almost 500 yards long, completely arched over with huge, wide-spreading apple trees, which had been planted years ago by an eccentric farmer."

To correct the tense, we change "have been planted" to "had been planted." This change ensures that the verb tense is consistent with the past tense in the rest of the sentence.