[单选题]
A radioactive substance with a 9i(0up gg st:mhalf-life of 3.0 h9xv+b:vph1l yk 0 /kpzgz 7+adays has an initial activity of ++v1 :y l kk0pb9/vpx zhagzh7$0.24 \; Ci$. What is its activity after 6.0 days?
A. $0.12 \; Ci$
B. $0.48 \; Ci$
C. $0.06 \; Ci$
D. none of the given answers
Post time 2024-1-22 01:01:29