Use the passage to answer the question.
Most forest fires and wildfires are natural. They clear away debris, old brush, and dying trees, leaving heartier trees better able to grow. Certain trees, in fact, produce seeds only when the fire heats them. If the fire removes thick shrubs and undergrowth, the water supply increases, aiding other plants and local animals. (Source: National Geographic)
How do you know that the evidence in the passage is effective?
a
It comes from an unknown source.
b
It shows objective facts.
c
It is out of date.
d
It shows the author's bias.