The isotope radon-222 has a half-life of $3.8$ days. Which statement is correct for a sample containing $1.0\,\text{mg}$ of radon-222?
- AAfter $1.9$ days there is $0.50\,\text{mg}$ of radon-222 left.
- BAfter $3.8$ days there is $0.50\,\text{mg}$ of radon-222 left.
- CIts half-life is half that of a $2.0\,\text{mg}$ sample.
- DThere is no radon-222 left after $7.6$ days.