Concept:The green colour of leaves comes from chlorophyll, a pigment that needs magnesium as a key structural component.
Explanation:Chlorophyll is the pigment that gives leaves their green colour.
It plays a central role in photosynthesis by absorbing sunlight.
Magnesium (
Mg) is located at the centre of the chlorophyll molecule.
Without magnesium, the plant cannot produce chlorophyll properly.
As a result, the leaves fail to stay green and may show yellowing.
Among the given nutrients, only magnesium is a direct part of chlorophyll.
Answer:B. magnesium