A （n) _____ is a chemical or electro－chemical attack on the metal surface which may be further increased if the sea－water is polluted.

Project ______is an uncertain event or condition that，if it occurs，has a positive or a neg

The temperature____________, the chemical reaction is being speeded up.A. raisedB. be

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There are_____I want to tell you.A．one or two thingsB．either one thing or another thingC．n

______ Chemical group is not explained in detail

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