Objective: Compute number of candidates who had none of the three.
Number of candidates who had none of the three = Total number of candidates - number of candidates who had at least one of three.
Total number of candidates = 400.
Number of candidates who had at least one of the three = n(A ∪ B ∪ C),
where A is the set of those who have a two wheeler, B is the set of those who have a credit card, and C is the set of those who have a mobile phone.
n(A ∪ B ∪ C) = n(A) + n(B) + n(C) - {n(A ∩ B) + n(B ∩ C) + n(C ∩ A)} + n(A ∩ B ∩ C)
Therefore, n(A ∪ B ∪ C) = 200 + 140 + 280 - {80 + 60 + 120} + 20
Or n(A ∪ B ∪ C) = 380.
n(A ∪ B ∪ C) is the number of candidates who had at least one of three.
As 190 candidates who attended the interview had at least one of the three,
(400 - 380 = 20) candidates had none of three.
Choice A is the correct answer.