The exposition introduces the reader to

Arrange the sentences below to form a logical paragraph. an experienced rock climber knows that it takes a combination of knowledge and preparation to perform a successful climb. a successful climb begins with a proper foothold, carefully placing each foot on a ledge or crack then reaching for a solid hold, and finally pushing off. in addition to a proper foothold, a climber must be careful to check the integrity of the rock before stepping because it has to be solid clear through. a veteran climber judges the integrity of the rock and chooses not to climb on conglomerates, packed clay with lots of little rocks. but, such knowledge of rock is not the only preparation a skilled climber needs; equally important is the correct equipment. with these tools, knowledge of rock composition and equipment safety, a climber may experience many safe and enjoyable climbs.

On november 17, 1968, football fans across the united states sat glued to their televisions. a close game between two top teams—the new york jets and the oakland raiders—was being broadcast. when the jets pulled ahead with only fifty seconds remaining, viewers went wild. but then, just as the raiders were bringing the ball across midfield, the game disappeared from the screen! in its place, a previously scheduled children's movie, heidi, started playing. callers flooded the tv network's phone lines, but it was too late. the raiders scored two touchdowns in the very final moments—touchdowns that were unseen by all but west coast viewers. as a result of the interrupted event, dubbed "the heidi game," television networks began delaying their regularly scheduled programs until football games had ended.

Which quotation best supports the authors’ claim and purpose?