What is the regulatory significance of IMO MSC Circular 981 in relation to the Titan investigation, and what did the TSB recommend regarding it?

A. MSC Circ. 981 provides guidelines for design, construction and operation of passenger submersible craft, but is non-binding unless incorporated into national law; TSB recommended both that Canada advocate for it to become mandatory at IMO level, and that Canada itself require compliance with it for all human-occupied submersibles connected to Canada

B. MSC Circ. 981 is a mandatory SOLAS chapter that OceanGate breached, exposing it to direct IMO sanction

C. MSC Circ. 981 only applies to submersibles exceeding 500 GT, so Titan was correctly exempted

D. MSC Circ. 981 was withdrawn in 2020 and replaced by the BWMS Code

A. A sphere distributes external hydrostatic pressure evenly across its surface, avoiding stress concentrations

B. A sphere is cheaper to manufacture from carbon fibre

C. A cylindrical hull cannot be pressure-tested before sea trials

D. A sphere allows a higher passenger capacity for the same hull weight

A. They were never validated to confirm they matched the theoretical values used in the original design

B. They exceeded design specification and provided an additional safety margin

C. They were validated by an independent classification society prior to first dive

D. They matched design values but degraded only after the fifth dive