What is the musical form for a piecenof music with two alternating sections section a and section b?

satin. 

"very shiny satin may look great in the fabric store or in the sewing room, but once onstage it can look fake and cheap as it reflects the light from the fixtures."

renascimento comercial, que, a partir do século 11, inaugurou definitivamente a baixa idade média, que se estenderia até o século 15.