Stability of reactant will be maximum for which value of $K$?

In which of the following cases does the reaction go farthest to completion?

Which one of the following statements is correct?

In the chemical reaction $A \rightleftharpoons B$,the system will be known to be in equilibrium when:

If some $He$ gas is added to the equilibrium $PCl_{5(g)} \rightleftharpoons PCl_{3(g)} + Cl_{2(g)}$ at constant pressure and temperature,the equilibrium constant of the reaction will....

For the reaction $A + B \rightleftharpoons C + D$,the equilibrium constant is $K$. If the initial moles of $A$ and $B$ are $1.0 \ mol$ each,what will be the value of the equilibrium constant in a second experiment under the same conditions if the initial moles of $A$ and $B$ are $2 \ mol$ and $3 \ mol$ respectively?