实际中，采用压扩技术实现非均匀量化，先进行压缩量化，再进行均匀量化，以达到非均匀量化的目的。
A. 对
B. 错
They haven't formally ___________ their engagement yet.
A. announce
B. announced
C. announcing
D. been announced
They ____________ that the flight would be delayed.
A. announced
B. announcing
C. announces
D. are announced
The _________ of gases such as carbon dioxide should be stabilised at their present level...
A. emission
B. emissions
C. many emission
D. many emissions
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