The correct option is B 6.89 M
Let mass of the solvent be 1000 g.
So, 4 m NaOH solution means 4 mol of NaOH in 1000 g solvent.
We know, molar mass of NaOH=40 g/mol
Hence 4 mol of NaOH=160 g
Total mass of solution = mass of solution + mass of solvent=(160+1000) g
Given, density of the solution =2 g/mL
So, the volume of the solution 11602 mL =580 mL=0.58 L
∴Molarity M=number of moles of solutevolume of the solution in L = 40.58=6.89 M