单项选择题

According to Peter Ward's research, _________.

A．90% of animals and plants went extinct 250 million years ago
B．dinosaurs died off as a result of meteor impacts
C．the "Great Dying" has much to do with volcanic activity
D．global warming played a minor part in the "Great Dying"

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热门试题

单项选择题

The greenhouse effect resulted hundreds of million years ago when _________.

A．the atmosphere changed dramatically
B．oxygen levels on the earth became lower
C．the sea levels became lower greatly
D．the sediment gave off enormous carbon and methane

单项选择题

It is implied in the last paragraph that _________.

A．only those lived near sea could survive
B．lack of oxygen led to the extinction of most of the species
C．The living space was too small to hold so many species
D．Global warming is related to human activities