vertical sea wall

sea wall with batter

stepped sea wall

sea wall with concave face

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not a correct explanation of A.

A is true but R is false.

A is false but R is true.

marine railways, dry docks, floating docks, wet docks

dry docks, wet docks, floating docks, lift docks

wet docks, floating docks, lift docks, marine railways

wet docks, lift docks, marine railways, dry docks

groynes

sea walls

revetments

moles

when the dock is empty

when the dock is empty with the ship of maximum tonnage

when the dock is full of water

when the dock is dry and is under construction