Here's a problem to solve: Betsy wants to find out if the rainfall in her town contains pollutants. The best way for Betsy to gather this information would be to collect

Among the 4 following options, which is the correct answer?

- A: one sample on one rainy day.
 
- B: one sample a day on several rainy days.
 
- C: several separate samples on one rainy day.
 
- D: several separate samples on several rainy days.
 