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 [atomic masses of K & Cl are 39 & 35.5 g mol^$-$1 respectively], is 'x' g ml^$-$1. 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 with temperature.

In the light of the above statements, choose the correct answer from the options given below :

1. A Both (A) and (R) are true and (R) is the correct explanation of (A). Correct answer
2. B Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. C (A) is true but (R) is false.
4. D (A) is false but (R) is true.