When a solute is present in trace quantities,the following expression is used:

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: At $10^{\circ} C$,the density of a $5 \ M$ solution of $KCl$ is given. The solution is cooled to $-21^{\circ} C$. The molality of the solution will remain unchanged.
Reason $R$: The molality of a solution does not change with temperature as mass remains unaffected by temperature.
In the light of the above statements,choose the correct answer from the options given below:

What is the molarity of a solution containing $0.8 \ g$ of $NaOH$ (molar mass $40 \ g \ mol^{-1}$) in $150 \ cm^{3}$ of water?

Assertion: One molal aqueous solution of glucose contains $180 \, g$ of glucose in $1 \, kg$ water.
Reason: Solution containing one mole of solute in $1000 \, g$ of solvent is called one molal solution.

The molarity of the solution obtained by mixing $800 \ mL$ of $0.5 \ M$ $HCl$ and $200 \ mL$ of $1 \ M$ $HCl$ will be ....... $M$.

How many grams of $CH_3OH$ should be added to water to prepare $150 \ mL$ solution of $2 \ M \ CH_3OH$?