What must happen to the nozzle and containers for certain liquids to ensure safe transfer?

To ensure safe transfer of certain liquids, it is essential that the nozzle and containers be electrically interconnected. This practice is vital because it helps to prevent the accumulation of static electricity, which can pose a serious hazard, especially with flammable liquids. When liquids are transferred, particularly at higher flow rates, static charges can build up due to friction, and if not properly grounded or interconnected, this static charge could result in a spark, leading to potential fires or explosions.

Electrical interconnection allows for a path to dissipate static electricity safely, thus reducing the risk of ignition during the transfer process. It is part of a comprehensive approach to safe handling practices in environments dealing with hazardous materials.

While other factors like grounding (the first option) are also important, here, the focus is specifically on the method of electrical interconnection to mitigate the risks associated with static electricity during liquid transfers.