In preparing a cargo space for receipt of a shipment of bagged cargo，which instruction for laying dunnage should be followed? （）
- AUse either 1 or 2 tiers of dunnage，spacing the pieces in each tier a foot apart，and lay pieces in the bottom tier diagonally to the ship's side
- BUse 1 tier of dunnage，laying the pieces tightly together to form a solid floor over the steel deck
- CUse 2 tiers of dunnage，spacing the pieces in the bottom tier about a foot apart and the pieces in the top tier 6 inches apart
- DUse 2 tiers of dunnage，spacing the pieces in the bottom tier about a foot apart and the pieces in the top tier together