Chemical Equillibria Comparisons
You have already ruled out the equations b, c, and e.


  But I'm not sure how to compare the remaining two reactions.


Have a look at equation a again.

The reaction of $\ce{P4O10}$ with water generates phosphoric acid ($\ce{H3PO4}$), which is a fairly strong three-protonic acid ($\mathrm{pK_{a1} = 2.16; pK_{a2} = 7.21}$). 

As a result, subsequent deprotonation of phosphoric acid
$$\ce{H3PO4 + H2O &lt;=&gt; H3O+ + H2PO4-}$$ 

will pull the equilibrium in equation a to the right.

Hydrogen sulfide ($\ce{H2S}$), on the other hand, is a rather weak acid with $\mathrm{pK_{a} = 7.0}$. Consequently, you will find a significant amount of undissociated hydrogen sulfide in aqueous solution. Therefore, the correct answer in the comparison is indeed d.