A scientist was studying a population of fish in a
pond over a period of 10 years. He observed that
the population increased each year for 3 years,
and then remained nearly constant for the rest of
the study. The best explanation for this
observation is that the population had
(1) stopped reproducing
(2) reached carrying capacity
(3) mutated into a different species
(4) run out of food and migrated to a different
pond