For a first-order radioactive decay with half-life $t_{1/2}$ and mean life $\tau$, which statements are correct?

1. AThe time required for $90\%$ of the sample to decay is $3.32t_{1/2}$.
2. BAfter a time equal to $\tau$, about $63.2\%$ of the sample has decayed.
3. CThe time required for $99\%$ decay is $6.64t_{1/2}$.
4. DAfter a time equal to $\tau$, the activity is $50\%$ of its initial value.