可能需要具备工作场所有害物质信息系统WHMIS，危险货物运输t DG，和安全实践的课程认证。
Certification in workplace hazardous materials information system (WHMIS), transportation of dangerous goods (TDG), and courses in safety practices may be required.
一个良好的安全实践是在测量之前假设所有位置电路上都存在危险电压。
A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring.
无知的育种实践可以产生不安全，危险狗只。
Ignorant breeding practices can produce unsafe, dangerous dogs.
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