Answer : 4. "2.6 g of solute in 2 ml of solution"
Explanation :

Answer: D) 2.6 g of solute in 2 ml of solution Explanation: A concentrated solution will contain the most solute molecules per solvent molecules. Here in the given options, 1)  6/10 = 0.6 2) 20.5/50 = 0.41 3) 30/120 = 0.25 4) 2.6/2 = 1.3   Hence, option D) is most concentrated.