A. 4

**B. 5 (Correct)**

C. 6

D. 8

E. None of these

Explanation:

If Bilal gives ‘x’ marbles to Arslan then Bilal and Arslan would have V – x and A + x marbles.

V – x = A + x — (1)

If Arslan gives 2x marbles to Bilal then Arslan and Bilal would have A – 2x and V + 2x marbles.

V + 2x – (A – 2x) = 30 => V – A + 4x = 30 — (2)

From (1) we have V – A = 2x

Substituting V – A = 2x in (2)

6x = 30 => x = 5.