What material goes between the primary receptacle and the secondary packaging?

The correct answer is that the material required between the primary receptacle and the secondary packaging is an absorbent material capable of absorbing the entire specimen. This is essential in the transportation of dangerous goods because it provides a safety measure in case the primary receptacle leaks or breaks during transit.

The absorbent material not only contains any leaked substances but also minimizes the risk of exposure to hazardous materials, ensuring that they do not spill out and potentially cause harm to individuals or the environment. This precaution aligns with safety regulations aimed at reducing the risk associated with transporting dangerous goods.

While cushioning materials like bubble wrap are useful for protecting containers from physical damage during transportation, they do not serve the critical function of containing spills, making absorbent material a necessary component in situations where hazardous liquids or substances are involved. Insulating materials and reflective materials have specific applications too, but they do not provide the vital capability to absorb and contain any leaks that may occur.