Which of the following pairs of compounds can be stable while retaining the identity of each compound in the pair over a period of time? I. $$\text{FeCl}_3$$ and $$\text{SnCl}_2$$. II. $$\text{HgCl}_2$$ and $$\text{SnCl}_2$$. III. $$\text{FeCl}_2$$ and $$\text{SnCl}_2$$. IV. $$\text{FeCl}_3$$ and KI.

A

I only

B

I and III

C

III only

D

II and IV