The pass percent of the water quality after sewage treatment in Weigang Combination Station in 2003is only70%, which forms the severe threat on the stratumlayer' s safety.
These layers are called strata and a single layer is called a stratum.
这些岩层被称作地层(strata)(stratum的复数形式), 单个岩层称为stratum。
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"When we are in the bath and we have been there for a while the stratum corneum [outer] layer of our skin expands," says Evans. "This causes wrinkles and means our fingerprints will be enlarged also."