Simplify the expression. begin expression . . begin fraction . . 6 times, x raised to the eighth power . . over . . 3 times, x raised to the second power . . end fraction . . end expression a begin expression . . 2 times, x raised to the fourth power . . end expression b begin expression . . 3 times, x raised to the fourth power . . end expression c begin expression . . 2 times, x raised to the sixth power . . end expression d begin expression . . 3 times, x raised to the sixth power . . end expression