根据以下材料，回答题
The Book of Life
So far， scientists have named about 1.8 million living species （物种）， and that"s just a small part of what probably exists on Earth. With so many plants， animals， and other creatures covering the planet， it can be tough to figure out what type of spider is moving up your leg or what kind of bird is flying by.
A soon-to-be-launched Web site might help. An international team of researchers has announced the creation of a Web-based Encyclopedia （百科全书） of Life （EoL）. The project aims to catalog every species on Earth in a single， easy-to-use reference guide.
To get the encyclopedia started， the creators will use information from scientific databases （数据库） that already exist. And eventually， in special sections of the site， nonscientists with specialized（专门的 ）knowledge will get to join in. Bird-watchers， for example， will be able to input which birds they"ve seen and where. The technology for this kind of tool has only recently become available.
As the EoL develops， you might find it useful for school projects. The site will feature special pages for kids who are studying ecosystems （生态系统） in their neighborhoods. To make sure the encyclopedia is accurate， scientists will review much of the information added to it. People who visit the site will be able to choose to leave out pages that haven"t been reviewed.
Another convenient feature of the EoL is that you"ll be able to pick the level of detail you see to match your interests， age， and current knowledge. If you wanted to learn about bears for a science class report， for example， you could use the "novice" setting to get basic information about the animals. On the "expert" setting， on the other hand， you could get much more detailed information about the history， literature， and exploration of bears.
It now takes years for scientists to collect all the data they need to describe and analyze species. The creators of the Encyclopedia of Life hope that their new tool will speed that process.
"Spider" and "bird" mentioned in Paragraph 1 are examples to illustrate __________. 查看材料

A. animals are people"s friends
B. there are numerous living species on Earth
C. it is easy to see spiders and birds
D. there are many types of spiders and birds