Organelles lacking internal ribosomes

Steps:

• Identify ribosomes' locations: free in cytoplasm, attached to rough ER surface, or inside certain organelles.
• Examine endoplasmic reticulum (1): Ribosomes bind externally to rough ER membrane, not enclosed within its lumen.
• Examine Golgi body (2): Lacks ribosomes entirely; functions in protein modification without protein synthesis machinery.
• Examine chloroplast (3): Houses 70S ribosomes in stroma for synthesizing chloroplast proteins.
• Examine mitochondrion (4): Contains 70S ribosomes in matrix for mitochondrial protein synthesis.

Why C is correct:

• C identifies 1 and 2 only, matching the definition that ER and Golgi lack internal or enclosed ribosomes, unlike semi-autonomous organelles.

Why the others are wrong:

• A includes 4, but mitochondria contain their own ribosomes per endosymbiotic theory.
• B includes 3, but chloroplasts contain 70S ribosomes for organelle-specific synthesis.
• D lists 3 and 4, both containing ribosomes as self-replicating structures.

Final answer: C