An engineer adds a gamma-emitting tracer to liquid in a buried pipe. The pipe is flushed with clean liquid. Tracer that escaped through a leak remains in the soil. The table shows readings taken afterwards. The background count rate is 20 counts per minute.
| Position | Count rate in counts per minute |
|---|---|
| P | 24 |
| Q | 23 |
| R | 180 |
| S | 22 |
Which conclusion is supported by the results?
The leak is near R because tracer remains outside the pipe.
The leak is near P because its reading is above background.
The leak is near S because most tracer has decayed there.
The leak is near Q because less radiation escapes there.