本题目来源于试卷: Half-life and decay constant，类别为 美国物理杯赛(Physics Bowl)
[单选题]
94.24: A sample of radioactive materyyfevyt v /gq)*9zp7 9ik2l lk mt40wvcd03t4t3;/sm f/an wvlal has an initial activity of 10,000 counts/minute. 30 minutes later, its activity is 2,500 counts/minute. The half-life of the material i33mmt d/4 vw0 vaftcl4s02nkt/l;kl ws:
A. 7.5 minutes
B. 10 minutes
C. 15 minutes
D. 20 minutes
E. 22 minutes
参考答案: C
本题详细解析:
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