Identifying cellular structures by biochemical components

Steps:

• Examine table for presence of DNA: all except possibly virus have it variably.
• Check for ribosomes: chloroplasts and mitochondria have 70S; bacteria have 70S; viruses lack them.
• Identify membrane and wall: bacteria have cell walls; others do not.
• Match to options: P as organelle with chlorophyll-related molecules, Q lacking ribosomes, R with mitochondrial DNA, S as prokaryote.

Why B is correct:

• Chloroplast (P) has thylakoid proteins, virus (Q) has only nucleic acid, mitochondrion (R) has mtDNA and 70S ribosomes, bacterium (S) has peptidoglycan and plasmids, matching standard biochemical profiles.

Why the others are wrong:

• A: Misplaces virus and bacterium, ignoring virus's lack of ribosomes.
• C: Duplicates mitochondrion, contradicting unique organelle traits.
• D: Starts with virus for P, which has photosynthetic molecules absent in viruses.

Final answer: B