Classifying unicellular organism as eukaryotic

Steps:

• Examine diagram for key organelles: presence of nucleus and mitochondria, absence of cell wall.
• Recall prokaryotes lack nucleus; eukaryotes have membrane-bound nucleus.
• Confirm organism fits eukaryotic criteria due to nucleus.
• Eliminate options contradicting definitions of cell types.

Why A is correct:

• Prokaryotes are defined by absence of nucleus; presence of nucleus confirms eukaryotic nature.

Why the others are wrong:

• B: Plants are eukaryotic and contain mitochondria for energy production.
• C: Eukaryotes like fungi and plants have cell walls; lack of wall does not determine eukaryotic status.
• D: Unicellular eukaryotes include protists, not just bacteria.

Final answer: A