Read the text and answer questions

Two Alaskan Kodiak bears joined a small circus where the pair appeared in a nightly parade pulling a covered wagon. The two were taught to somersault, to spin, to stand on their heads, and to dance on their hind legs, paw in paw, stepping in unison. Under a spot-light the dancing bears, a male and a female, soon became favourites of the crowd. The circus went south on a West Coast tour through Canada to California and on down into Mexico, through Panama into South America, down the Andes the length of Chile to those southernmost isles of Tierra del Fuego. There a jaguar jumped a juggler, and afterwards, mortally mauled the animal trainer; and the

shocked show people disbanded in dismay and horror. In the confusion the bears went their own way. Without a master, they wandered off by themselves into the wilderness on those densely wooded, wildly windy, subantarctic islands. Utterly away from people, on an out-of-the-way uninhabited island, and in a climate they found ideal, the bears mated, thrived, multiplied, and after a number of generations populated the entire island. Indeed, after some years, descendants of the two moved out onto half a dozen adjacent islands; and seventy years later, when scientists finally found and enthusiastically studied the bears, it was discovered that all of them, to a bear, were performing splendid circus tricks.

On nights when the sky is bright and the moon is full, they gather to dance. They gather the cubs and the juveniles in a circle around them. They gather out of the wind at the center of a sparkling, circular crater left by a meteorite which had fallen in a bed of chalk. Its glassy walls are chalk white, its flat floor is covered with white gravel, and it is well-drained, and dry. No vegetation grows within. When the moon rises above it, the light reflecting off the walls fills the crater with a pool of moonlight, so that it is twice as bright on the crater floor as anywhere else in that vicinity. Scientists speculate that originally the full moon had reminded the two bears of the circus spotlight, and for that reason they danced. Yet, it might be asked, what music do the descendants dance to? Paw in paw, stepping in unison what music can they possibly hear inside their heads as they dance under the full moon and the Aurora Australis, as they dance in brilliant silence?