Flying over the rugged terrain, the explorers spotted an ancient ruin through their binoculars.

The correct answer to the question "Flying over the rugged terrain, the explorers spotted an ancient ruin through their binoculars." is Option B: As the explorers flew over the rugged terrain, they spotted an ancient ruin through their binoculars..

The other options — A) The explorers, flying over the rugged terrain, spotted an ancient ruin through their binoculars., C) An ancient ruin was spotted by the explorers flying over the rugged terrain through their binoculars., D) Through their binoculars, flying over the rugged terrain, the explorers spotted an ancient ruin. — are incorrect for this GMAT Exam Prep question. As explained above: The introductory phrase 'Flying over the rugged terrain' correctly modifies 'the explorers'. Option B clarifies this relationship by turning it into a subordinate clause, which is grammatically preci…