Complete the sentences with the correct phrases.
Robert played drums in a band but never saw himself as a talented singer. Then, at a concert, the soloist for the band's big song was missing. Robert ___without thinking. He _____across the stage to the microphone and started singing. When he finished, the audience burst into applause. Robert realized that he had _____He was a much better singer than he had believed before. underestimated his talent acted instinctively propelled himself​