A.
A conventional wide body aircraft will have a larger HOLD, smaller COMPARTMENTS within a HOLD, a BAY (or POSITION) or SECTION subdividing the COMPARTMENT. In the DGR, they mainly refer to HOLD and COMPARTMENT.

A “HOLD” is a space confined by ceiling, floor and 4 walls used for carrying load; a “COMPARTMENT” is a space within a HOLD; a “BAY” or “POSITION” is a subdivision of a unitized/palletized compartment, i.e., ULD POSITION; and a “SECTION” is a subdivision of a non-unitized compartment, i.e, the net section of a bulk compartment.

Therefore a wide bodied freighter will have a large Main Deck HOLD, and in the Lower Deck, there are 2 HOLDS, i.e., FWD and AFT HOLD. The FWD HOLD is subdivided into 2 Compartments, namely FWD 1 and FWD 2. The AFT HOLD is subdivided into 3 Compartments, i.e., AFT 3, AFT 4 and the BULK Compartment.

A BAY or POSITION is a subdivision of a unitized (containerized/palletized) HOLD or COMPARTMENT indicating ULD Positions. A SECTION is a subdivision of a non-unitized compartment, i.e., the Bulk Compartment.