Double-membrane organelles in cells

Steps:

• Recall that double-membrane structures include nucleus, mitochondria, and chloroplasts.
• Examine labeled structures: assume P is nucleus and Q is mitochondrion based on typical diagrams.
• Confirm single-membrane structures like R (endoplasmic reticulum) and S (Golgi apparatus).
• Select pair matching double-membrane definition.

Why A is correct:

• Nucleus and mitochondria are defined as having two lipid bilayers for protection and function.

Why the others are wrong:

• B includes S (single membrane, like Golgi).
• C includes R (single membrane, like ER).
• D pairs two single-membrane structures.

Not enough information on exact labels without diagram.

Final answer: A