1 The wаy emperоr penguins cаre fоr аnd prоtect their unhatched eggs is one of the wonders of nature. 2 The only land creatures able to survive the Antarctic winter, these birds must care for their young while withstanding 24-hour darkness, gale-strength winds, and temperatures of 60 to 80 degrees below zero. 3 Each year, at the start of the Antarctic autumn, female emperor penguins each lay a single egg on bare ice. 4 Then, after transferring care of the eggs to their mates, they take off across the open ice for the nearest fishing site. 5 The males spend the next 60 days with neither food nor light, living off their considerable body fat and balancing the eggs on their feet under a protective flap of skin. 6 During this time, they adapt to the brutal temperatures by huddling together in flocks of hundreds. 7 Although penguins are unable to fly, they are superb swimmers. 8 If all goes well, the females return from the sea with a meal of fish just as the eggs are hatching. Which of the following numbered sentences of the passage best expresses an opinion rather than a fact?