Identifying molecules with inherent multiple C=C bonds

Steps:

• Recall structures: triglycerides have fatty acid chains; proteins like collagen and haemoglobin have amino acid backbones plus functional groups.
• Check double bonds: saturated fats have none; unsaturated have C=C in chains; collagen has peptide bonds (no C=C); haemoglobin's heme is a porphyrin ring.
• Evaluate "at least two": requires structure guaranteeing ≥2 C=C, not just possible.
• Compare options: only haemoglobin's heme consistently has multiple conjugated double bonds.

Why D is correct:

• Haemoglobin's heme group features a porphyrin ring with at least 11 conjugated C=C double bonds, per its chemical structure.

Why the others are wrong:

• A: Unsaturated triglyceride may have only one C=C if monounsaturated in a single chain.
• B: Collagen is a protein with peptide bonds and no C=C double bonds in its triple-helix structure.
• C: Saturated triglyceride has all single bonds in fatty acid chains, zero C=C.

Final answer: D