单项选择题

The most versatile ______ embryonic stem cells, which ______ found in the embryo at the earliest stage of development and can grow into any part of the body.

A．are, are
B．is, is
C．are, is
D．is, are
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单项选择题
And while we ______ have a great deal of trouble adjusting to a climate that gets 2 degrees centigrade warmer over the next century, an ice age by mid-century--be unimaginably devastating.
A．might, could
B．could, might
C．would, might
D．might, would
单项选择题
Because it takes longer to install and involves some tinkering to get it to work just right, it's best for more experienced users. But, oh, what joy! ______ a detailed log of every ad it annihilates, ______ it makes a satisfying 'thunk' when it nabs one.
A．Not only Killer keeps, but also
B．Not only does Killer keep, /
C．Only Killer keeps, and
D．Only if Killer keeps, /
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