Answer :
*A is 3 times B, thus B is smaller than A,
B = A/3
So B can be 1,2 or 3 as A is less than 10.
*Difference between B and D is 2
D can be either B+2 or B-2.
*If B=1 or 2, D will be B+2 (as B-2 is -1 and 0, but we know that D is a positive integer). C will be D-1 or B+1. So B will be smallest.
If B=3, then D will be either 1(B-2) or 5(B+2).
C is one less than D, thus C is smaller than D.
C is 0 or 4. But all are positive. So C is 4.Therefore D=5.
So,B(3)