occur now and then 中文意思是什麼
occur now and then
解釋
時在出現-
The burst accidents of environmental pollution occur now and then. there a qreat need for improving the prevention and management of the accidents. aneacly warning system of environmental pollution should be established
突發性環境污染事故時有發生,因此有必要提出事故預防和管理水平,應建立突發性環境污染事故的預警系統。
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