If a population's location prevents new members from entering their area, this would be an example of:
O geographic isolation
O natural selection
O competition
O reproductive isolation

9.9 years

a = p(1 + rt) . . account balance after time t at rate r starting with principal p

3000 = 2500(1 + 0.0202t) . . filling in the given numbers

1.2 = 1 + 0.0202t . . divide by 2500

0.2 = 0.0202t . . . subtract 1

0.2/0.0202 = t ≈ 9.901

it will take about 9.9 years for the account balance to reach $3000.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.