A.≤0.5mg/lB.<0.5mg/lC.<0.5μg/lD.≤0.5μg/l
A.3.6μs.cm-1B.5.1μs.cm-1C.1.3μs.cm-1D.1.1μs.cm-1
A.5.1μs.cm-1B.5.4μs.cm-1C.4.3μs.cm-1D.3.6μs.cm-1