皮皮学，免费搜题
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【单选题】
指示剂一般分为酸碱指示剂，氧化还原指示剂和金属指示剂，（）是金属指示剂。A.
溴酚蓝
B.
二甲酚橙
C.
亚甲基蓝
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皮皮学刷刷变学霸
举一反三
【单选题】Passengers on board aren't allowed _____ calls during take-off．
A.
making or receiving
B.
to make or receive
C.
to have made or received
D.
having made or received
【单选题】_______ has been announced, our government will take more measures to make the falling economics recover as soon as possible.
A.
That
B.
As
C.
It
D.
What
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