The graph gives the recorded count rate of radiation from a source that contains a radioactive isotope. The detector is in a laboratory and there is no shielding against background radiation. What is the recorded count rate after one half-life?
- A$\frac{X}{2}$
- B$\frac{Y}{2}$
- C$\frac{(X - Y)}{2}$
- D$\frac{(X + Y)}{2}$