Four letter-clusters have been given out of which three

Solution

The logic followed here is as follows, From the left end, First letter + 2 = Fourth letter Place value of the 2nd letter, when written as per English alphabetical order, is equal to the place value of the third letter, when written as per reverse alphabetical order. In option a: L + 2 = N, Place value of S = Place value of H In option b, Y + 2 = A, Place value of F = Place value of U In option c, E + 2 = G, Place value of T = Place value of G In option d, K + 2 = M, Place value of Z ≠ Place value of B