safety classes of building structures 建筑结构安全等级
Electrical safety classes 安全级别
safety classes of structure 结构安全等级
Safety Requirement Classes 安全要求等级
"We went to the hazmat safety classes, and you have one guy telling you you don't want to be in it.
VOA: standard.2010.05.06
Sometimes they're reluctant to take part in important training such as fire safety classes and child identification programs, which guard against abduction.
VOA: standard.2010.07.22
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