CAT Exam Model Paper 3 with solutions for free online practice

(d) In this case since x, y and z are distinct positive integers, our aim is figure out which of the answer choices cannot be expressed as the sum of 3 integers uniquely. For eg. 6 can only be expressed as (1 + 2 + 3). 7 can only be expressed as (1 + 2 + 4).
But 8 can be expressed as either (1, 2, 5) or (1, 3, 4).
Hence, option (d) is the correct option.