Question

What is the main factor that prevents the growth of tropical plants in the northern part of the United States?

A) Predators
B) Overpopulation
C) Pollutants
D) Climate

Answer 1

I would say D but overall it would actually be all of the above :)

Answer 2

It would be D Climate because tropical plants need warmth and humidity they have to be in almost the same temperature all year long