For a binary nonideal $A-B$ mixture exhibiting a minimum boiling azeotrope, the activity coefficients, $\gamma_{i} \left ( i=A, B \right )$, must satisfy

1. $\gamma _{A}> 1,\gamma _{B}> 1$
2. $\gamma _{A}< 1,\gamma _{B}> 1$
3. $\gamma _{A}= 1,\gamma _{B}= 1$
4. $\gamma _{A}< 1,\gamma _{B}< 1$