Step 1: Understanding the elements in the list
Manganese (A): Involved in the splitting of water in photosynthesis (iii).
Magnesium (B): Important for the synthesis of RNA and DNA (i).
Sulphur (C): A constituent of cysteine and methionine (ii).
Hydroponics (D): Used in the commercial production of lettuce (iv).
Final Answer:
A-iii, B-i, C-ii, D-iv