Cell structures containing RNA: nucleus, ribosomes, and mitochondria

Steps:

• Recall that RNA is synthesized in the nucleus (pre-mRNA, rRNA, tRNA).
• Note ribosomes contain rRNA and are sites of protein synthesis.
• Recognize mitochondria have their own ribosomes and RNA for energy production.
• Confirm structure 4 (e.g., cell wall or lysosome) lacks RNA.

Why B is correct:

• Option B includes structures 1 (nucleus), 2 (ribosomes), and 3 (mitochondria), all of which contain RNA as per eukaryotic cell biology definitions.

Why the others are wrong:

• A adds 4, which does not contain RNA.
• C omits 2 (ribosomes), a primary RNA site.
• D excludes 1 and 2, missing key RNA-containing structures.

Final answer: B