Final answer:
The word 'convoy' in the passage describes a group moving together through an orchard and is best defined as option A. A group.
Step-by-step explanation:
In the provided context, the word "convoy" is described as moving slowly through orchards, which suggests it is composed of vehicles or a group of people or entities traveling together. Therefore, the most likely meaning of "convoy" in this context is A. A group. The flat terrain and the visual of the convoy stretching as far as the eye can see supports this interpretation of the passage. The imagery of the sun begins to fade adds to the understanding that the convoy is on a journey through a vast landscape.