The equilibrium constant $K$ for the reaction $\ce{2HI <=> H2 + I2}$ at room temperature is $2.85$ and at $\pu{698 K}$ is $0.014$. This implies that:
a) $\ce{HI}$ is exothermic compound
b) $\ce{HI}$ is very stable at room temperature
c) $\ce{HI}$ is relatively less stable than $\ce{H2}$ and $\ce{I2}$
d) $\ce{HI}$ is resonance stabilized
I was getting both a and c (only one of the options is supposed to be correct). Which is the most appropriate answer?