【单选题】

That experience led RhettButler to begin writing a book about rainforests and threats to their existence.But he did not publish the book. Instead, in 1999, he used his research for the book to create a web site. The site is Mongabay.com. The name is spelled m-o-n-g-a-b-a-y.

RhettButler named the site for Nosy Mangabe, an island off Madagascar. His purpose was to inform the public about tropical rainforests.But the subject wideneD、A、former businessman, he became a respected writer of science and environmental stories.
The popularity of Mongabay.com attracted advertisers. Small ads on the site pay for its operations. Mongabay has grown and led to other sites. For example, there is a site for children, kids.mongabay.com.Another one, WildMadagascar.org, is all about the island nation that RhettButler calls his favorite place.
He travels the world on several major trips each year. His working tools are a laptop computer, cameras and sometimes diving equipment.
He often calls on experts for information for stories. For example, he interviewedAlison Jolly, a top expert on ring-tailed lemurs.And last week he wrote about another animal, the rare snow leoparD、He interviewed Rodney Jackson, a biologist who established the Snow LeopardConservancy.
Stories like these have made Mongabay a favorite place on the Internet for researchers, students and teachers. InApril, Time.com named it one of the fifteen top climate and environment web sites.
RhettButler says he is concerned about how the current economic crisis in the world might affect environmental conservation efforts. For example, he says the falling price of oil could reduce interest in developing solar power.But he also points to a recent United Nations report on "green jobs". The report said efforts to fight climate change might lead to millions of jobs in biofuels by two thousand thirty.
"Biologist" means______.A．an expert on animals
B．a person on plants
C．an expert on earth
D．an expert on health