单项选择题

The assumption _____ human cloning rests is that all genetic cells contain exact copies of the original set o9f genetic instructions.

A． on which
B．on that
C．at which
D． which
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单项选择题
Between 1890 and 1970 the monetary costs of supplying energy _____ more or less constant or declined.
A．to stay
B．was stayed
C．stayed
D．has stayed
单项选择题
The reward was not always given to everyone, nor _____ to those who deserved it most.
A．it was not given
B．was given
C．it was not given nor
D．was not it given
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