集合 a={1,2,3,4,5,6}，b={1,3,5,7,9}，则a&b的结果是? ( )
{1, 3, 5}
{2, 4, 6}
{1, 2, 3, 4, 5, 6, 1, 3, 5, 7, 9}
[1, 3, 5]