Over the last century, paleontologists have used small differences between fossil specimens to classify Triceratops into sixteen species. This classification is unjustified, however, since the specimens used to distinguish eleven of the species come from animals that lived in the same area at the same time. Which of the following, if true, would enable the conclusion of the argument to be properly drawn A: Not every species that lived in a given area is preserved as a fossil. B: At least one individual of every true species of Triceratops has been discovered as a fossil specimen. C: No geographical area ever supports more than three similar species at the same time. D: In many species, individuals display quite marked variation. E: (E) Differences between fossil specimens of Triceratops that came from the same area are no less distinctive than differences between specimens that came from different areas.

The proper reaction to the discovery of a fossil is:

People are beginning to use clean energy sources mainly because _______. A: fossil fuels have caused a lot of pollution B: clean energy is cheap C: fossil fuels have cost a lot of lives D: they do not have enough fossil fuels now

The burning of fossil fuels results in the pollution of the______.

It is predicated that existing reserves of fossil fuel ____________ by 2045.

What two effects does burning fossil fuel have?

什么叫化石（fossil）？研究化石的意义是什么？

The reconstruction of _____ species from fossil bones was often undertaken by museum workers.

Fossil fuels like coal, oil and natural gas are non-renewable energy sources.

There is a large amount of fossil fuel on earth, but the sun supplied a(n) (limit) __________ supply of energy.