A Sample of (Which Decays By $\beta$ -Emission)has an Activity of 10

Multiple Choice

A sample of (which decays by $\beta$ -emission) has an activity of 10.0 mCi.After 6.06 d it has an activity of 7.5 mCi.The half-life of ³²P is approximately

A) 3.03 d
B) 7.30 d
C) 12.1 d
D) 14.6 d
E) 24.2 d