The correct option is A 11, 21, 31, 51, 71, 81
Ascending order is arranging the numbers from the lowest to the highest.
When we compare the first digit of given numbers, we get to know that 1 < 2 < 3 < 5 < 7 < 8.
Hence, ascending order is 11, 21, 31, 51, 71, 81.