which of the following are examples of exponential decay

1) the population of a florida is increasing by 43% each year

2) the pesticide DDT has half life if 15 years

3) March madness has 64 teams in the bracket. Each round half the teams are eliminated

4) after an antibiotic is added to culture of bacteria, the number of bacteria is reduced by half every three hours

5) a tree frog population doubles every three weeks