We have to find the number of members in the final group when the groups are formed by 2 members max(pair).

So final group will either have 2 members or 1 member (leaving us with choice A and choice B).

For the first condition, assume that there is x number of the members in each group except final one. Total members= x*4+3

For the second condition, assume that there is y number of the members in each group except final one. Total members= y*5+3

x*4+3=y*5+3

4x=5y

the possibe integer values that can satisfy above equation are x=5, y=4 or x=10, y=8 or x=15, y=12

We are given that the number of the members should be between 24 and 57

the only value that satisfy above condition is x=10, y=8

total number of the members 10*4+3=43=> odd number, the number of members in the last group will certainly be 1

The correct answer is A.

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