The correct answer is B) Silver and copper are prohibited in the parts of valves and fittings in contact with the cargo. This is correct because the cargo, butadiene, is a compressed flammable gas. Regulations for the transportation of compressed gases require that materials in contact with the cargo must not contain silver or copper, as these metals can react with and degrade the cargo. The other answer choices are incorrect - A) is false as the cargo tank can be sampled at any time, not just during loading; C) is false as the shipping document only needs to specify the proper shipping name, not the exact quantity; and D) is false as there is no requirement to pad the ullage with compressed air at a minimum pressure of 2 psig for this type of cargo.