Assertion (A): $\mathrm{As}{}_2\mathrm{S}{}_3$ dissolves in yellow ammonium sulphide but $\mathrm{CdS}$ does not. Reason (R): $\mathrm{As}{}_2\mathrm{S}{}_3$ is an acidic sulphide that forms a soluble thio-anion with sulphide/polysulphide, whereas $\mathrm{CdS}$ is a basic sulphide.

1. ABoth A and R are true and R is the correct explanation of A
2. BBoth A and R are true but R is not the correct explanation of A
3. CA is true but R is false
4. DA is false but R is true