单项选择题
A.≤0.3B.≤0.6C.≤0.9D.≤1.1
A.≤0.2/1000B.≤0.4/1000C.≤0.6/1000D.≤0.8/1000
A.≤0.07B.≤0.05C.≤0.03D.≤0.01
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