Which solutions most concentrated ? 1) 0.1 mole of solute dissolved in 400 ml of solvent 2) 0.2 mole of solute dissolved in 300 ml of solvent 3) 0.3 mole of solute dissolved in 200 ml of solvent 4) 0.4 mole of solute dissolved in 100 ml of solvent

We can find out concentration of solution by dividing number of moles by volume.
Most concentrated solution is the solution with highest number of moles in a unit volume
Concentration = number of moles/ volume
1. 0.1 mol/ 0.4 L = 0.25 mol/L
2. 0.2 mol / 0.3 L = 0.67 mol/L
3. 0.3 mol / 0.2 L = 1.5 mol/L
4. 0.4 mol/ 0.1 L = 4.0 mol/L

From the given solutions most concentrated solution is 4th solution. In this the highest amount of solute dissolved in a unit volume is 4.0 mol. Therefore this is the most concentrated solution.

the answer is true.

this statement is true.

Most smaller stars don't have a radiative zone.