Alpha Particles hope this helps
Answer:

when there is a radical in the denominator, we should rationalize (mutiply the denominator and numerator by the radical) to get rid of the radical in the denominator.
I am going to go with,
0.10 g/mL
0.0700 g/mL
0.0447 g/mL
I don't know if this is the correct answer, but I am 80% sure that it may be.
:) :)
The simple formula is C = n/V
n = mols
C = Concentration or Molarity
V = Volume in Liters.
n = 2
V = 4
C = 2 / 4
C = 0.5 mol/Litre