The number of introduced species in the United States has increased dramatically since 1950. Which of the following factors has most strongly led to this increase? (3 points)

1) Accelerating climate change since 1950 is leading to one planetary habitat in which the strongest organisms survive and spread.

2) Increases in the human population and greater mobility since 1950 is allowing for more species to be transported to new habitats.

3) Intentional introductions of species have increased steadily since 1950.

4) We have more data now than we did previously and the increase is entirely explained by better documentation of introduced species.