Answer : 3. "28"
Explanation :

Answer: C) 28 Explanation: Three persons A, B, C can be arranged in a queue in six different ways, ie ABC, CBA, BAC, CAB, BCA, ACB. But since there are only 3 persons ahead of C, so C should be in front of the queue. Thus, there are only two possible arrangements, ie CBA and CAB.   We may consider the two cases as under: Case I:  ←3C↔8B↔5A→21   Clearly, number of persons in the queue = (3+1+8+1+5+1+21=) 40   Case II:  ←3C A↔5B   Number of persons between A and C                     = (8 - 6) = 2    ∵[C↔8B A→21B]   Clearly number of persons in the queue = (3+1+2+1+21) = 28   Now, 28 < 40. So, 28 is the minimum number of persons in the queue.