The Half-Life of Cobalt-60 Is 5

Multiple Choice

The half-life of cobalt-60 is 5.3 years,while that of strontium-90 is about 29 years.Suppose you have samples of both isotopes,and that they initially have the same activity (number of decays per second) .What must be true of the numbers of cobalt-60 and strontium-90 nuclei in these samples?

A) There are more strontium-90 than cobalt-60 nuclei.
B) There are equal numbers of cobalt-60 and strontium-90 nuclei.
C) There are more cobalt-60 than strontium-90 nuclei.
D) It is not possible to compare numbers of nuclei without knowing the masses of the samples.