Based on the Following Sorted 20 Values for Age, What

Based on the following sorted 20 values for age, what are the possible split points?
{20, 22, 24, 26, 28, 31, 32, 34, 35, 40, 42, 43, 45, 47, 49, 51, 52, 53, 55, 57}

A) {20, 21, 23, 25, 27, 29.5, 31.5, 33, 34.5, 37.5, 41, 42.5, 44, 46, 48, 50, 51.5, 52.5, 54, 56}

B) {21, 23, 25, 27, 29.5, 31.5, 33, 34.5, 37.5, 41, 42.5, 44, 46, 48, 50, 51.5, 52.5, 54, 56, 57}

C) {0, 21, 23, 25, 27, 29.5, 31.5, 33, 34.5, 37.5, 41, 42.5, 44, 46, 48, 50, 51.5, 52.5, 54, 56}

D) {21, 23, 25, 27, 29.5, 31.5, 33, 34.5, 37.5, 41, 42.5, 44, 46, 48, 50, 51.5, 52.5, 54, 56}