This question is based on the sequence of letters of the English alphabet. VD ⇒ ‘V’, 4th from the back and ‘D’,4th from the front. ZA ⇒ ‘Z’, 1st from the back and ‘D’,1st from the front. XC ⇒ ‘X’,3rd from the back and ‘C’ 3rd from the front. While in ‘By’,‘B’ 2nd from the front and ‘Y’, 2nd from the back.These options are different from other options.