单项选择题

Newly- found fossilized tracks in Alaska proved that dinosaurs' migration between Asia and North America took place ________.

A．much earlier than experts previously thought.
B．much later than experts previously thought.
C．after Asia became an independent continent.
D．sometime around 25 million years ago.
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单项选择题
The discovery of dinosaur fossil sites in Bolivia is eciting because of the following reasons ECEPT ________.
A．they are found in a continent other than Asia and North Continent.
B．the largest dinosaurs in the world are found in this discovery.
C．there are some unknown species of dinosaurs found this time.
D．the dinosaurs were believed to be some of the last ones on earth.
单项选择题
The discovery of a new type of ceratopsian dinosaur suggests ceratopsians ________.
A．migrated to North America around 70 - 80 million years ago.
B．arrived in Asia from North America about 90 million years ago.
C．originated in Asia and later migrated to North America.
D．could have moved to Asia from North America long ago.
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