Explanation:

In the given series

1st term has odd number starting from 11, So the Series is 11, 13, 15, 17, 19

2nd term has an alphabet follwed by its alpha numeric number in the order +4, +3, +2, +1.

So  the Series is M13, Q17, T20, V22, W23

Therefore, 15T20 is the answer.

Hence, option 4 is the correct answer.