A solute A associates in benzene as $2\mathrm{A}\rightleftharpoons {\mathrm{A}}_2$ with degree of association $\beta$, so $i=1-\beta /2$. Which of the following statements is/are correct?

1. AThe observed depression of freezing point is smaller than that calculated for non-associated A.
2. BFor complete association, $i=0.50$.
3. CThe observed elevation of boiling point is larger than that calculated for non-associated A.
4. DFor $\beta =0.40$, $i=0.80$ and the observed molar mass is $1.25$ times the normal molar mass.