Which of the following is present in the core of chlorophyll molecule?

Magnesium is present in the core of chlorophyll molecules.
Chlorophylls absorb light most strongly in the blue portion of the electromagnetic spectrum as well as the red portion.
The molecular formula chlorophyll is C₅₅H₇₀O₆N₄Mg and a structure of (2-formyl)-chlorophyll a was deduced based on NMR, optical and mass spectra.
Most chlorophylls bind magnesium, the axial ligands attached to the Mg²⁺ center are often omitted for clarity.