Eukaryotic cells feature membrane-bound organelles Steps:

• Define eukaryotic cells as those with a true nucleus and membrane-bound organelles, unlike prokaryotes.
• Examine structure 1: nucleus, a defining eukaryotic feature.
• Examine structure 2: mitochondria, for energy production in eukaryotes.
• Examine structure 3: cell wall or nucleoid, more typical of prokaryotes.
• Examine structure 4: endoplasmic reticulum, a membrane-bound organelle in eukaryotes. Why A is correct:
• Eukaryotic cells contain a nucleus (1), mitochondria (2), and endoplasmic reticulum (4) as standard membrane-bound structures. Why the others are wrong:
• B includes 3, a prokaryotic feature not universal in eukaryotes.
• C omits the essential nucleus (1) and ER (4).
• D omits the essential nucleus (1) and ER (4). Final answer: A