Which of the following is true of the capital gain tax rate in the U.S. from 1968 to 2007? Select one: A. It was at an all-time low level of 15% during the 1980s. B. It averaged around 30% from 2003-2007. C. It reached a peak of 40% in the 1970s. D. It remained constant at 10% in the 1990s