Questions below refer to the following article.
High among the many triumphs of man's courage and spirit is Walter Drake's and Olivier Vogel's (1)............... climb to the summit of Mount Everest without oxygen tanks in 1967.
Although several attempts to climb Everest without additional oxygen had been made in the past, none had been successful. Drake and Vogel began moving cautiously up the south ridge towards the summit, which they reached after a grueling climb at 10:30. They lingered (2)............... on the summit and then began the tiring climb down the mountain. They said it was the (3)............... test of endurance they had ever experienced.