单项选择题

Nowhere in nature is aluminum found free, owing to it always ______ with other elements, most commonly with oxygen.

A．being combined
B．having combined
C．to combine
D．combined
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单项选择题
Nowadays Internet enables us to know things happen almost at the exact moment ______.
A．which they are happening
B．they are happening
C．which they happen
D．they have happened
单项选择题
There is no person ______ is always in the right.
A．who
B．that
C．which
D．whom
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