Given series: MPCT ZPTC BETA ZETA UIMO 1) On changing each letter to next letter in the words as English alphabetical series NQDU AQUD CFUB AFUB VJNP 2) Clearly, 2 words have only one vowel in it. NQDU, CFUB Note: In English alphabetical series there are 5 vowels i.e. A, E, I, O, U else all are consonants. Hence, two is the correct answer.