What did Peak realize about his climbing ability?

• A. He had only climbed skyscrapers at sea level and needed better lung capacity for the thin air.
• B. He had trained in high-altitude environments before with great success.
• C. He could climb mountains with minimal oxygen if he kept a steady pace.
• D. He was naturally buoyant and could float over ice.

Answer: (A)

The idea being tested is how altitude changes what it takes to climb—and what Peak recognizes about his own limits. In the story, Peak has mostly climbed skyscrapers at sea level, where air is plentiful. When he faces real mountains, he realizes that thin air at high elevations makes breathing harder and taxes the body more quickly. To tackle those climbs, you need stronger lung capacity and the ability to acclimate to lower oxygen, something he hadn’t prepared for by his prior city-climbing experiences.

So the best choice says he had only climbed skyscrapers at sea level and needed better lung capacity for the thin air. That captures the contrast between his past experience and what high-altitude climbs demand. The other options don’t fit the situation: one suggests successful high-altitude training that isn’t part of his story, another implies easy adaptation to low-oxygen conditions, and the last is unrelated.