In which environment would you expect a deposit of rock salt or rock gypsum to have formed

Rock salt and gypsum are formed in environments with high evaporation of salt water such as shallow sea.

They are minerals found in bays, shallow seas, estuaries, and dry lakes. Gypsum may form large crystals and it is found as a mineral or gypsum rock.

Gypsum chemical composition shows the presence of calcium and sulfate ions to mention a few and this resonates with the area where they are formed.   They form when there is evaporation from ocean water with high calcium and sulfate content.

Rock salt otherwise halite occurs due to the evaporation of chloride and sodium ions from ocean water. These two minerals are associated with one another.

iii. and iv. only is the right answer