Components A and B have normal boiling points of $80^{\circ }\mathrm{C}$ (A) and $100^{\circ }\mathrm{C}$ (B). They form a binary mixture showing large positive deviation from Raoult's law, with a minimum-boiling azeotrope of boiling point $70^{\circ }\mathrm{C}$ containing $60\%$ B by mole. A liquid mixture containing $30\%$ B by mole is subjected to fractional distillation with a very efficient column at constant pressure. Which outcome is expected?

1. APure A distils over first and pure B is left in the flask
2. BPure A distils over; the azeotrope is left in the flask
3. CPure B distils over first; the azeotrope is left in the flask
4. DAzeotrope (60% B) distils over first; pure A is left in the flask