单项选择题
A.2t1/2=t1/2′ B.t1/2=2t1/2′ C.t1/2=t1/2′ D.t1/2=4t1/2′
A.43.29sB.15sC.30sD.21.65s
A.t1/2=t1/2′ B.t1/2〉t1/2′ C.t1/2〈t1/2′ D.两者大小无法确定