What is NOT a requirement of cargo piping installed in tank vessels carrying grade D or E cargo ONLY?

Correct Answer: Option D — The cargo piping system shall be fixed.

Under 46 CFR, tank vessels carrying only Grade D or E cargoes do not strictly require a fixed piping system, unlike vessels carrying lower flashpoint flammable liquids (Grades A, B, or C), which mandate fixed installations. Flexible hoses or portable piping arrangements are sometimes permissible under specific conditions.