The dancers wear bright Western costumes that blend into swirls of color as they melt from one pattern into another. On stage, a gentleman taps his left boot and calls: "Do-si-do and then you promenade your partner as you go rollin', rollin', you're rollin' down the river ..."

You can picture this scene at a grange hall where farmers have gathered for their weekly hoe-down. But today, this activity is equally at home in a San Carlos gymnasium or even the Oakland Auditorium. Square dancing has moved into the suburbs and cities. There are eight square dance clubs in San Francisco alone.

Surprisingly, this dance is of comparatively recent vintage. Although its roots go back to European folk dancing, the square dance didn't evolve until the last century as a uniquely American folk dance form.

Q. Underline the sentence which supports the correct answer to question No. 1.