单项选择题

A．hold
B．fix
C．keep
D．retain
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单项选择题
The first A3XX will be available in 2003.
A． Right
B． Wrong
C． Not mentioned
单项选择题
What leads to the formation of a black hole
A．The structure of a star.
B．A collision between two stars.
C．The attraction of two large stars.
D．The shrinking of a large star by its own gravitational force.
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