Two sealed sources each contain 1.0g of a pure radioactive isotope. Source R has a half-life of 2.0h, while Source S has a half-life of 20h. Which statement best describes their activities immediately after preparation?
a) The two sources have equal activities because each contains the same mass of radioactive material.
b) Source S has the greater activity because its nuclei are more stable and therefore more numerous.
c) Source R has the greater activity because its shorter half-life gives it a larger decay constant.
d) Source R has the smaller activity because its nuclei disappear so quickly that very few decays occur each hour.